What is herd immunity, and how does it relate to pediatric vaccination uptake? US parent perspectives

Accepted Manuscript What is herd immunity, and how does it relate to pediatric vaccination uptake? US parent perspectives Elisa J. Sobo PII:

S0277-9536(16)30296-9

DOI:

10.1016/j.socscimed.2016.06.015

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Social Science & Medicine

Received Date: 9 January 2016 Revised Date:

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Accepted Date: 10 June 2016

Please cite this article as: Sobo, E.J., What is herd immunity, and how does it relate to pediatric vaccination uptake? US parent perspectives, Social Science & Medicine (2016), doi: 10.1016/ j.socscimed.2016.06.015. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Manuscript number: SSM-D-16-00082R1

Article title: What is herd immunity, and how does it relate to pediatric vaccination uptake?

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US parent perspectives

Author: Elisa J. Sobo, Department of Anthropology, San Diego State University, San Diego, California,

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USA.

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Corresponding Author Information: Professor EJ Sobo [email protected] Department of Anthropology San Diego State University

San Diego, CA 92182-6040

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Telephone: +1-619-594-6591

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5500 Campanile Drive

Acknowledgments: This institutionally approved research (IRB#950089) was supported in part by a

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grant from San Diego State University’s President’s Leadership Fund. Interviewers Arianna Huhn, Autumn Sannwald, and Lori Thurman contributed to the initial data analysis. Haley Chasteene, Berhana Eyob, Thomas Friday, Soujanya Gade, Allison Hillis, Leann Jensen, Scott Johnson, Kelsey Jorgensen, Lindsay Klein, Susan Madruga, Mali Mccormack, Nancy Mendez, Raquel Perez, Amanda Piccus, Natasha Reeder, Matthew Schneider, Lauren Sit, Anna Steiner, James Turner, Ana Vargas, Jill Varney, Kyrstin West, Bobbie Yarbrough—students in my spring 2014 medical anthropology course—contributed to data collection with ethics board approval and administrative assistance from Lori Thurman. Jane-Ann

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Carroll of SDSU’s Children’s Center and managers of various organizations frequented by vaccine-

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cautious parents enabled recruitment. Thanks are due to all.

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What is herd immunity, and how does it relate to pediatric vaccination uptake?

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US parent perspectives

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Abstract - In light of current concern over pediatric immunization rates, 53 US parents with at

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least one child kindergarten age or younger were surveyed and interviewed regarding vaccine

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decision making. Data were collected in 2014 in San Diego, California. Herd immunity was not a

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salient issue: only six (11.3%) referenced the term or concept spontaneously; others had to be

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prompted. Parents familiar with herd immunity (70%) variously saw it as not just unnecessary

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but unproven, illogical, unrealistic, and unreliable. For instance, parents questioned its

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attainability because many adults do not immunize themselves. Some understood the concept

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negatively, as an instance of “herd mentality.” Further, having knowledge of herd immunity that

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public health experts would deem ‘correct’ did not lead to full vaccination. Implications of

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findings for understanding how the public makes use of scientific information, the potential role

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of public health messaging regarding altruism and ‘free-riding,’ and assumptions that vaccine-

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cautious parents would willfully take advantage of herd immunity are explored in relation to

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parent role expectations and American individualism.

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Key Words - Herd Immunity; Community Immunity; Immunization; Vaccine Hesitancy;

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Tragedy of the Commons; Health Literacy

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Research Highlights

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Prior knowledge and experience affect how parents conceptualize herd immunity

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Understandings regarding herd immunity can actually undermine intent to vaccinate

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Low perceived civic connectedness makes herd immunity irrelevant to vaccinators

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A view of others as unreliable undermines belief that herd immunity can be achieved

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Vaccination messaging should leverage parents’ wish to stand apart from ‘the herd’

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1. Introduction

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1.1. The Problem

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Although certain vaccinations are required for US kindergarten entrance, a small but rising

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number of parents file PBEs—personal belief exemption waivers—to enable enrollment for un-

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and selectively-vaccinated children without medical or religious justification (Omer, Richards,

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Ward, & Bednarczyk, 2012; Omer, Salmon, Orenstein, Dehart, & Halsey, 2009; Wang, Clymer,

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Davis-Hayes, & Buttenheim, 2014). In California, where this research occurred, 1.9% of

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kindergarteners had PBEs on file in 2008-09, compared to 2.8% in 2012-13 (Lee & Abanilla,

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n.d.).

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With increased vaccine caution, community-level or ‘herd’ immunity to certain vaccinepreventable diseases (VPDs) can be undermined, leading to outbreaks (Omer et al., 2009;

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Sugerman et al., 2010). Public health entities often refer to this hazard in promoting vaccination;

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for an example, see the California Department of Public Health “Why Immunize?” webpage

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(https://www.cdph.ca.gov/programs/immunize/Pages/WhyImmunize.aspx).

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Quadri-Sheriff and colleagues reviewed, systematically, all Medline literature through 2010 to better understand “the role of herd immunity in parents’ decision to vaccinate children”

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(2012: 522). They found only 29 studies (17 qualitative, 12 quantitative) asking parents about

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vaccinating their children for the “benefit to others” (p.523). In these, only 1% to 6% of parents

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spontaneously named herd immunity or the broader construct (benefit to others) as a primary

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reason for vaccination. This helps explain why the limited research on how real-life pediatric

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vaccination intent is affected by messages emphasizing benefits to society suggests that such

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messaging is not actually very effective (e.g., Hendrix et al., 2014; see also Hershey et al., 1994;

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and for experimental or theoretical treatments, see Betsch, Böhm, & Korn, 2013; Buttenheim &

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Asch, 2013; Hershey, Asch, Thumasathit, Meszaros, & Waters, 1994).

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Knowing that herd immunity has little salience for parents considering pediatric vaccination does not mean, however, that we know the whole story. We must determine why it is

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irrelevant here—and we must ask how and why it may be relevant in other regards.

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We do know that parents, who by-and-large do not think of herd immunity when

considering vaccinating their own children, may deploy it in other contexts: for instance, Skea

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and colleagues (2008) found herd immunity being “hotly debated” in an online parenting chat

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forum they observed, particularly in terms of “who bears the burden and for what benefit”

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(pp.1388,1385). There are also indications that the ways parents deploy the construct, when they

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do, may be different to the ways public health experts think of it. For example, Downs, Bruin,

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and Fischhoff (2008) found that parents, when pushed to use the construct in a ‘mental models’

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study, referenced its incorrectly perceived importance for disease eradication—not its value in

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prevention and control.

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How common are such disconnections? What other reworkings are made, and why? What outcomes might parents’ alternate understandings support? In attempting to answer such

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questions, my research not only confirms prior findings regarding herd immunity’s irrelevance to

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pediatric vaccination campaigns, adding weight to the still-small literature. It explores, in more

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depth than previously achieved, how parents deploy the herd immunity construct. It does so

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using focused interview and survey data collected from 53 Californian parents in 2014.

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1.2. Public Health Viewpoint

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In the public health viewpoint, ‘herd immunity’ means that “the risk of infection among

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susceptible individuals in a population is reduced by the presence and proximity of immune

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individuals” (Fine, Eames, & Heymann, 2011: 911). This depends on maintaining the threshold-

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proportion of VPD-immune individuals in a population that, given randomized population-wide

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vaccination and social mixing, will suppress transmission and proliferation of the VPD in

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question.

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The science behind herd immunity is complicated, however. There are many

contingencies and the broad public health assertion that proximity to immunized people confers

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protection to those who are not or cannot be immunized often breaks down at the level of

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implementation. This is in part because vaccination itself does not always confer immunity.

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Also, immunity following most vaccines wanes, so sustaining the necessary level of protection

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through all relevant transmitting age groups can require repeated doses over the life course.

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Further, even where population-level immunity for a given VPD is attained (i.e., where overall

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vaccine uptake rates meet the threshold), outbreaks still can happen if non-random pockets of

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people do not vaccinate.

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Concurrently, the individual costs of vaccinating (e.g., time, money, risk for injury) rise relative to the proportion of vaccinated individuals. At some point individual costs exceed

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immediate, self-perceived, individual benefits. This paradox can lead to a ‘tragedy of the

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commons’ in which some individuals take advantage of community-provided goods by ‘free-

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riding’: they forgo vaccines themselves, reaping the benefit of herd immunity without bearing

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any personal costs (Buttenheim & Asch, 2013).

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1.3. Social Science Viewpoint

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Although the public health justification for vaccination rests on community benefits, the social

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science of pediatric vaccination has, perhaps particularly in the US, highlighted individual

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responsibilities and rights. Kaufman, for instance, showed parents exercising a culturally

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constructed ‘right to choose’ through vaccine decisions while simultaneously coping with “the

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burden of responsible consumption” fostered by the “structural conditions of life in postindustrial

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society” (2010: 23, 9). Individualized ‘risk assessment’ and ‘risk management’ have become a way of life due to a perceived breakdown of ‘expert systems.’ Present structural conditions have

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created vulnerability, stimulated doubt, and magnified feelings of individualized responsibility

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(p.27; see also Beck, 1992; Giddens, 1991). Faircloth notes that this is reflected in how “‘parent’

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has shifted from a noun denoting a relationship with a child (something you are), to a verb

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(something you do)” (2010:2.5).

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Reich shows further how gendered expectations exacerbate parenting concerns for

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women, holding them as “uniquely accountable” for child health (2014: 699). Mothers can thus

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see themselves by definition (i.e., in light of gender ideology) as not only better-qualified than

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various institutions to optimize their children’s health, but duty bound to do so: ‘good’ mothers

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must invest in their children’s well-being and protect them from potential harms—including

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those of public health interventions.

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All this is intensified in the US by neoliberal values favoring open markets, deregulation, and individual liberty and initiative. The self-centered, competitive outlook encouraged leads

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mothers—at least those with socioeconomic means—to view technologies (vaccination included)

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in terms of benefits to the individual, not the community. This is in direct opposition, as Reich

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(2014) also notes, to the public health framework’s collectivism.

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1.4. The Present Project

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In this environment, one might expect frequent vaccine free-riding. However, to free-ride in a

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consciously strategic manner, vaccine non-conforming parents must know at least a modicum

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about how herd immunity works and they must trust other citizens to immunize. Do they? Do

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parents even engage with the herd immunity concept when making vaccine decisions? If so,

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which parents and how?

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2. Methods

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Data Collection and Analysis

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In 2014, with ethics approval from San Diego State University (SDSU), data were collected from

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English-speaking parents with at least one child kindergarten age or younger. Because better-

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educated parents are overrepresented among those filing PBEs (Reich, 2014; Shaw,

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Tserenpuntsag, McNutt, & Halsey, 2014; Wei et al., 2009), participants were recruited from

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SDSU’s daycare center. Because non-vaccination is relatively rare even in this demographic,

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community locations within San Diego known to attract vaccine-cautious individuals (e.g.,

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health food stores) also were targeted. A convenience sample was used because: the project was

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hypothesis generating versus hypothesis testing, there were privacy concerns at the main

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recruitment site, and other forms of sampling were impossible at the secondary sites (e.g.,

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markets). Participants, who provided data in private settings such as the daycare center’s break

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room or a local coffee shop, received $25 gift cards.

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Data collection involved first the completion of a few short structured surveys (see Sobo

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et al., 2016). Most relevant in this analysis were the demographic and child vaccination status

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surveys. The former asked for such things as parent age, number of children, income, and

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ethnicity; the latter asked whether a parent’s youngest child was fully up-to-date for, partially up

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to date for, or had never been vaccinated with each vaccine on the state’s list.

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Participants also completed the 12th grade ‘Evaluate Sources and Information’

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component of the Tool for Real-time Assessment of Information Literacy Skills (TRAILS; Kent

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State University Libraries, 2014), which has 10 multiple-choice questions. This component was

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selected because the highest degree most US citizens attain is for the 12th grade, according to

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census data (Anonymous, 2013). Moreover, in contrast to, for instance, the plagiarism avoidance

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component, it measures how well an individual can assess the validity of sources such as those

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that parents doing their own research into vaccination might come across. This is a crucial skill

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for such parents (see Sobo et al., 2016). TRAILS components are validated, widely used, and

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easier and quicker to administer than many other such assessments.

Data were collected on paper, entered after the fact by the interviewer, and double-

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checked by an assistant. Some participants requested their paper-and-pencil surveys to complete

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at home prior to their data-collection meeting, to save themselves time. Thus, a meeting could

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take as little as 15 minutes. Five lasted over one hour; but the mean duration was 32 minutes.

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Participants provided narrative data using a method adapted from Gottschalk & Gleser

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(1969) involving a single, focused, open-ended question: “How do you know you’ve made the

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right decision with regards to vaccinating your child/ren?” Two formal prompts were included:

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“What or who gives you confidence in your decision?” and “How does the health of the

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community or ‘herd immunity’ come into play?” Answers were audio-recorded and transcribed. Transcripts were analyzed using a theme-characterization protocol modeled on prior

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‘barriers to care’ work (Sobo, Seid, and Gelherd 2006; and see Hill, 2005; Quinn, 2005; Ryan &

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Bernard, 2003). First, as part of the larger study this article draws upon (Sobo et al., 2016), I and

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lead interviewers Ariana Huhn, Autumn Sannwald, and Lori Thurman sought to identify the

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range of issues parents raised. To protect against order-linked bias, we each reviewed transcripts

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in a uniquely randomized order. Like examples were compared across cases and disconfirming

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examples sought. Discrepancies were resolved through inspection and discussion of negative

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cases and rival classifications. Upon saturation, we had identified major themes (categories) and

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sub-themes (items) as well as their relationships. Then, for this analysis, I took a new pass at the

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transcripts, focusing on references to ‘herd immunity’ in name and concept (e.g., in references to

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helping society, protecting babies, or free-riding). Several more themes were identified. Lay knowledge of herd immunity expressed in the interviews was thus described in

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inductively-derived codes. Although those were my primary focus, to assist in exploring lay

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frameworks I examined parent knowledge in relation to the public health framework also,

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classing parent knowledge as ‘none,’ ‘in name only,’ ‘general,’ and ‘delineated.’ While the first

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two classifications indexed parental indifference to public health thinking on herd immunity, the

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latter two indicated some regard for it. Participants with ‘general’ public health knowledge knew,

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as indicated in their narrative discourse, that higher vaccination rates in a population lead to

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fewer VPD cases (e.g., “herd immunity … means ‘oh if everybody else is vaccinated, my child

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won’t get sick’” [Alicia; names are pseudonyms]). Those with ‘delineated’ public health

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knowledge discussed the mechanism that public health messaging posits as underlying herd

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immunity (i.e., lowering the chances that a pathogen can gain a foothold from which to spread by

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ensuring that most bodies are immune to or unable to host said pathogen), and/or mentioned

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classes of vulnerable individuals who might benefit particularly (e.g., babies, the immune-

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compromised).

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Quantitative vaccination status scores were derived from survey self-reports regarding the

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focal (youngest) child’s uptake of the five vaccinations required for kindergarten entry in

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California: chicken pox (varicella); hepatitis B; measles, mumps, rubella (MMR); polio; and

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diphtheria, tetanus, and pertussis (DTaP). Other quantitative data (e.g., household income,

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TRAILS scores) were analyzed using standard descriptive statistics.

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3. Findings

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3.1. Sample Description

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Participants’ median income was $100,000, as compared to the local median of $64,000. They

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were also relatively well educated: all had at least a high school degree; one third had completed

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a bachelor’s; another third had a master’s; just over one-tenth had doctoral degrees. The majority

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lived with a partner. Most (n=49; 92.5%) were female; many (n=31; 58.5%) were White.

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Twenty-five participants were community recruits. As expected, they were overrepresented in

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the vaccine non-conforming groups, but indistinguishable otherwise.

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[INSERT TABLE 1 HERE]

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The average child age was about three years-old; the focal (youngest) child in each

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family was just over two years-old on average. The average parent was, therefore, in the thick of

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the pediatric vaccination process.

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As Table 1 shows, twenty focal children were either selectively or not at all vaccinated. Vaccine status scores, from which these groupings were derived, correlated inversely with the

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degree to which each parent saw vaccines as a risk (Pearson correlation coefficient = 0.72).

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Selectively vaccinated children’s vaccination status scores ranged from 1 to 8 (0 = none; 10 =

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completely up to date; no child scored 9). The mean, however, was 2.9: very few vaccines had

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been taken on average. The most frequently foregone vaccine was for varicella; the least

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frequently foregone was the DTaP. Of all the variables quantitatively measured, the only notable

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between-group differences in the narrative data conformed to vaccine status.

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3.2. Self-education

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Parents’ ideas about herd immunity nested into understandings regarding parental accountability.

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Being a ‘good’ parent included safeguarding one’s children’s health and this was seen to require

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self-education.

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Parents often pointed to prior educational achievements as proof that they were prepared

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to self-educate (e.g., “I’m college educated” [Paul]). In regard to the process itself, Mirasol, a 35

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year-old Filipina with a two-parent household income of $125,000, and one unvaccinated two

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year-old child, reported:

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We used the CDC [and doctor-recommended sources]... We did independent research.

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What we did was, started with just a general—a Google search. So, Doctor Google, so to

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speak… it will give you a list of things that you can go to search. So we would go—we

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obviously didn’t go through all of them, because there’s thousands and thousands. But we

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tried to pick several different ones from both points of view. You know, obviously,

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they’re skewed one way or another. There is—there is no study that I have found that is

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completely balanced. It’s like politics: you never find anything that is completely

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balanced. So we tried to look at both sides, and tried to give both a very fair, you know,

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presence.

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Many but not all parents investigated as energetically. Those least proactive were most

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likely to be full or up-to-date vaccinators (see Sobo et al., 2016). Up-to-date parents often

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mitigated the general obligation to self-educate by relying on expert systems, and casting

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vaccination as “routine.” As Jane remarked, “I just went with the package”; as Maria observed,

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“Well I take her to the pediatrics and I trust that they know what they're doing.”

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3.3. Public Health Herd Immunity Knowledge

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The public health construct of herd immunity was not important to most parents—at least not

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until asked. Only six (11.3%) mentioned herd immunity spontaneously; two of the six did not

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use the term but referenced the concept through talk of community benefit. One of the six had

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vaccinated her child partially; one was a non-vaccinator; four were full vaccinators. Three of the

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six mentions were positive; the other three were negative, in ways soon discussed.

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Parents who did not mention herd immunity spontaneously in name or concept (i.e., the majority) received the herd immunity prompt. As Table 2 indicates, 16 of the 53 parents (30.2%)

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were totally unfamiliar with the phrase. For instance, full vaccinator Daniella responded to the

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prompt with “How do you spell that? Sorry.” Cynthia asked, “The concept of what?” Another

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twelve (22.6%) parents were familiar with the phrase but ‘in name only.’ As Heather said, “I’ve

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heard that but I don’t know what—I’m guessing it’s [pause]; yeah, I don’t know.”

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[INSERT TABLE 2 HERE]

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All non-vaccinators were in the combined ‘none’ plus ‘in name only’ knowledge group

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(see Table 2). So were 18 of the 33 full vaccinators (54.5%). However, only 4 in 13 selective

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vaccinators (30.8%) were similarly unversed.

The rest of the parents (45.3%) did have some public health knowledge regarding herd

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immunity, mostly in ‘general’ (28.3%) but also in ‘delineated’ form (17.0%). Full vaccinator

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Amanda had ‘delineated’ public health knowledge—and assumed (concordant with popular

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discourse) that vaccine-cautious people lack this. She said,

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It’s silly when people say like ‘If vaccines worked so good, then why are you concerned

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with my child not getting vaccinated?’ That’s the kind of anti-vax mentality. But I think

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what people don’t realize is that vaccines aren’t a hundred percent. There’s people who can’t get vaccinated.

‘Delineated’ public health knowledge was not, however, the sole purview of full

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vaccinators (see Table 2). For instance, Christina, who used a “delayed schedule,” explained

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vaccination “protects the herd so that the people that are weak like the elderly or the super

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young, like my infant, who [is not] vaccinated, are protected by the herd.” A much smaller

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proportion of full vaccinators had that level of understanding. Indeed, selective vaccinators had

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the most public health knowledge of all three subgroups. Notably, and although the sample size

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and research design prevents inferring significance, selective vaccinators also had the highest

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information literacy scores on average (see Table 3).

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[INSERT TABLE 3 HERE]

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3.4. Herd Immunity Knowledge More Broadly

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A focus on parental grasp of public health knowledge ignores other herd immunity knowledge

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that parents possess and apply—knowledge that may be key to better understanding and serving

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vaccine-hesitant parents. Many parents with ‘correct’ knowledge shared additional information.

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Even parents who recognized herd immunity ‘in name only’ knew non-standard things about it—

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things that affected uptake. Only full vaccinators were likely really to know nothing at all.

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Key herd immunity-related themes raised by parents are enumerated in Table 4; they are

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organized into positive, neutral, and negative registers. Importantly, the latter was fullest and

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knowledge there was most unconventional. Also, themes were not always mutually exclusive;

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but each parent generally stuck to one register. It bears repeating that fully vaccinating parents

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had the least to say, perhaps because, as John reported, “it seemed pretty routine’; or as Paula

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noted, “I just took [the doctor’s] word for it.”

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[INSERT TABLE 4 HERE]

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3.4.1. Positive and Neutral Themes. Vaccinators who viewed herd immunity positively generally

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saw it in keeping with public health messaging as a SOCIAL GOOD, and as a PREVENTATIVE

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process. Some mentioned their own contribution to herd immunity, demonstrating themselves as

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GOOD CITIZENS.

But these were never primary reasons for vaccinating: herd immunity was an

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ANCILLARY benefit

of an individualist action.

Some selective vaccinators felt this way too. Nicole, for instance, explained,

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I think more about the other details: how it directly affects [my child’s] body, first; our

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family, second; and herd immunity is probably like, hmmm, fourth or fifth on the list of

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things I would consider. I understand the importance of it… but that’s not my main

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priority.

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The divergent agendas of the collectivist public health approach and the individualist approach

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of parents were articulated by Lisa: “I think the health profession are trying to do more for the

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best of everybody, and I think the parents are trying to do more what’s best for their individual

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child, and that’s probably the conflict right there.”

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Some parents were so individualistically focused, and parentally obligated, that they did

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not see the conflict; for them, herd immunity was IRRELEVANT. Parents in all groups said so but

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selective- and non-vaccinators explained why in most detail, perhaps due to heightened levels of

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vaccine-related health-consumer activation. For example, after confessing, “I don’t really

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concern myself with what’s going on in the community,” non-vaccinator Brooke clarified:

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As long as our family is doing what we can to take care of ourself—to make sure our

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immune system is strong… even if we are exposed to other people, I’m not very

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concerned about it… . [We] have been exposed to someone who had mumps, and… twice to people with chicken pox… no issues have arisen from that… . I really do think that it is individual—there’s a lot of individual responsibility with making sure your system is working properly.

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3.4.2. Negative Themes. The bulk of relevant discourse was more negatively tinged. Take for

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instance the notion that herd immunity was UNNECESSARY. As Michelle said, “I don’t feel that

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we are in an area that vaccine preventable diseases are necessarily a threat to [my daughter’s]

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well-being.” She and others argued that because VPDs have been eradicated or controlled,

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pushing people to contribute to herd immunity is duplicitous if not just overkill. That a disease’s

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low incidence has to be maintained was not considered.

Some reported that herd immunity was UNPROVEN anyhow. For instance, non-vaccinator

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Crystal said, “Diseases have natural cycles they go through like even polio. They do wax and

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wane on their own. A lot of the vaccine companies and research pro-vaccine like to take credit

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for the waxing and waning of these diseases and I’m not certain that that’s the case.”

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Beside misattributing causality, claims for herd immunity could be just plain ILLOGICAL. As Crystal also noted, “even vaccinated children can and do contract these viruses that they are

313

vaccinated against so that argument didn’t stand for me very well.” Selective vaccinator Angela

314

put it succinctly: “Herd immunity is a bunch of crap.” She had given her child one vaccination,

315

and might give others, but not because of herd immunity: “Within my research I found that herd

316

immunity is not real.”

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Sometimes herd immunity was thought bogus because of, in Michelle’s words, “adults not being vaccinated.” Therefore, herd immunity was—even if logical in theory—UNREALISTIC

319

in practice. If, Michelle asked, “we only vaccinate for so many years and then stop, how do we

320

truly have real herd immunity?” Christina said, “It’s not just specifically the unvaccinated kids

321

that are causing outbreaks of illnesses but it’s actually also older adults that aren’t vaccinated

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anymore.”

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Herd immunity also could be UNRELIABLE. For instance, after saying she’d “seen the

324

effects of some of these diseases that can be prevented” full vaccinator Shannon stated, “We

325

didn't want to rely on herd immunity.” A notable hesitance to rely on others for keeping one’s

326

children safe and the related need for self-reliance was expressed by many as they justified

327

things like doing “independent research” (Mirasol) and remaining alert to how doctors might be

328

“swayed by pharmaceutical companies” (Stephanie).

A few parents said that herd immunity was, by definition, EXPLOITABLE. Full-vaccinator

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Alicia said, “[Herd immunity] means ‘Oh if everybody else is vaccinated, my child won’t get

331

sick.’” However, acting on such knowledge through non-vaccination was frowned upon. Mark,

332

another full vaccinator, said “herd immunity, for me, has something of a negative connotation.”

333

Megan, a selective vaccinator herself, claimed that free-riders are “racist,” because “when they

334

go to India or Africa they suddenly want to vaccinate their kids.”

No parent explained his or her own vaccination non-conformity as exploitative, making

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manifest how neoliberal individualism can neutralize any sense of responsibility to others,

337

naturalizing exploitation or unmarking it. Alternately, vaccination non-conformity reflected

338

divergent boundary definitions: for example vaccine-delaying parent Christina pushed aside the

339

question of exploitation with a counter-definition of vaccination’s lower age limit, subsuming

340

her child into the category of vulnerable individuals entitled to the community’s protection.

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Some parents from every group saw reliance on herd immunity as DEMEANING: exploiting

342

it meant a lack of self-reliance; as well, the phrase implied a sheep-like mentality. Selective

343

vaccinator Ana noted, “I feel like a lot of people make just blind—they just follow because

344

they’re told ‘Oh we’re gonna do this,’ and they just do it… . I wanna make my own decisions… .

345

I don’t care what everybody else does.”

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For some, however, total self-determination was impossible because herd immunity is

346

SELF-PERPETUATING:

348

necessity, at least for older children. For instance, herd immunity lowered the chances that Ana’s

349

selectively-vaccinated son would “run into someone else that has chicken pox.” Although she

350

wanted him to catch chicken pox from others, she did not want that to happen “when he gets

351

older, when it can damage something else that’s way more life threatening than when he’s

352

three.”

353

4. Discussion

354

This research supported and extended the limited prior (yet often programmatically unheeded)

355

findings indicating that invoking herd immunity does not increase pediatric vaccination rates.

356

Not only did participants have little ‘correct’ public health knowledge of herd immunity;

357

decisions to vaccinate reflected concern for one’s child’s health—not the herd. Moreover, most

358

parents unversed in herd immunity (as experts define it) vaccinated anyway.

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high levels of vaccine uptake, they said, have increased vaccination’s

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By refusing to confine itself to an a priori, public health view on what counts as herd immunity knowledge, this research also demonstrated that the range of parent understanding is

361

broader than previously recognized—and that many ideas parents hold abut herd immunity

362

actually challenge the public health message. Another novel finding was that the most

363

knowledgeable, most information-literate parents were vaccine-selective non-conformers.

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While committed non-vaccinators are difficult prospects (Kahan, 2013; Nyhan, Reifler,

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Richey, & Freed, 2014), targeting selective vaccinators can lead to high returns (see Leask,

366

2011). The high interest in self-education shown by the selective vaccinators in this study

367

suggests that they may welcome informational interventions—and findings provide new clues as

368

to what kinds of information might be most helpful. The fact that selective vaccinators already

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had more ‘correct’ information on herd immunity than full vaccinators confirms that simply

370

providing ‘more’ information is not enough (see also Leach & Fairhead, 2007).

371

Anthropologists have long promoted culturally appropriate messaging; Mark and Mimi Nichter’s work on increasing community demand for vaccination and other public health goods

373

by leveraging local perceptions provides a fine example. Nichter and Nichter advocate tailored

374

interventions attending to the fine-grained details of what people already do to protect child

375

health, and using culturally-appropriate analogies to better contextualize health education

376

information being shared (1996). Similarly, “customization based on patient needs and values”

377

and positioning the patient as “the source of control” has been recommended for the US by the

378

Institute of Medicine (2001: 8).

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Nonetheless, shifting the parameters of engagement “beyond compliance [toward]

380

partnership” (Nichter and Nichter 1996: xvii) is still a work in progress here. Partnership efforts

381

are complicated by high rates of Internet and social media use, and by how many past expert

382

safety assurances (e.g., regarding DDT, asbestos, cigarettes, antibiotics) have been upended. This

383

lowers some parents’ tolerance for crude public health claims regarding herd immunity (as

384

shown earlier, the complicated science behind herd immunity is not reflected in what public

385

health experts would term ‘correct’ knowledge).

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Policymakers who view parent skepticism as a barrier rather than a legitimate position to

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be addressed do so at peril. For instance, California’s authoritarian move to simply outlaw

388

PBEs—i.e., to focus on compliance versus partnership—may lead not only to intensified grass-

389

roots activism in support of vaccine caution but also to more home schooling as vaccine-cautious

390

parents work around statutory constraints. Other workarounds reported anecdotally include using

391

one’s social network to locate doctors willing to sign medical waivers. Applying for a

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conditional waiver (which allows school attendance for children not fully vaccinated due to

393

access-related or timing issues on the condition that full vaccination be sought and achieved) also

394

may work. As the ban looms, the state has in fact seen an increase in such waivers, 90% of which

395

may have been inappropriately granted (Aliferis, 2016).

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With all this in mind, I discuss the findings’ implications for two modes of culturally sensitive information provision. I also examine how participants’ view of society might affect

398

herd immunity information uptake, and what it might portend for other approaches discussed

399

given the low risk most US children have for VPDs today.

400

4.1. Redirecting Extrapolations

401

One approach to partnered information provision anticipates how prior knowledge or

402

experiences across the life-span may derail public health recommendations as parents extrapolate

403

from antecedent contexts to new ones. For example, parents who had learned that children must

404

get booster shots, or that immunity to certain diseases is not life-long, fit those understandings to

405

knowledge they already had that adults don’t get boosters. Accordingly, they concluded that

406

most adults are no longer immune—and therefore that herd immunity was “not real.”

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This argument has some basis (Mossong & Muller, 2003). Although immunities to

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measles, mumps, rubella, and varicella-zoster persist for life, some antibody responses are less

409

durable: diphtheria has an estimated half-life of about 19 years; tetanus, about 11 (Amanna,

410

Carlson, & Slifka, 2007). Factors affecting durability include whether immunity is exposure or

411

vaccine-induced and (if the latter) exact vaccine formulations.

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It will be helpful, therefore, to provide anyone worried about immunity’s longevity with

vaccine-specific and locally relevant statistics. Moreover, information regarding adult immunity

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414

might be disseminated and public health outreach undertaken to ensure that adults who do need

415

boosters can get them.

416

Another example of a reasonable extrapolation that partnered information provision might address is when parents who understand that vaccines ‘work’ figure that vaccinated people

418

have no reason to shun unvaccinated individuals, and that herd immunity is unnecessary (i.e.,

419

that one is either vaccinated and so 100% protected, or one is not). Provision of detailed, non-

420

patronizing, community-vetted information regarding the relationship of vaccines to full

421

immunity (which does not always result), the link between individuals’ achieved immunity rates

422

and population-level or herd immunity, and the ways in which particular vulnerable populations

423

such as the immune-compromised gain protection from immune community members could be

424

helpful here.

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Community vetting has already been used productively to increase the transparency, accountability, local relevance, and feasibility of a small number of vaccination programs (e.g.,

427

Marshall et al. 2014). While community vetting groups are somewhat akin to focus groups, the

428

preferred term, ‘public deliberation,’ emphasizes a civic aspect. Accordingly, vetting (or

429

‘deliberative’) groups, sometimes even called ‘juries,’ often comprise citizens representing the

430

at-large public. This is the approach Marshall and colleagues took. But juries—or ‘consultative

431

panels’—also can be made up of ‘consumers’ (those targeted to receive the kind of intervention

432

in question) or of ‘advocates’ (experts or partisans) (Degeling, Carter, and Rychetnik 2015).

433

Given the particulars of pediatric vaccination, a deliberative group that includes parents with

434

small children who vaccinate selectively and those who vaccinate fully but with hesitation may

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be most productive (see also Leask 2011).

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436

Of course even the most culturally-sensitive information provision efforts may falter given the polarization promoted through unconsidered media reporting and vaccine advertising

438

(Kahan, 2013). Moreover, outreach may backfire if the focal vaccine has been implicated in a

439

recent vaccine injury scare, if information manifests vested interests (e.g., through funding

440

disclosures), or if self-educating parents are not allowed to come to their own conclusions, for

441

instance with the support of decision-aids. Here it is worth noting that parents’ conclusions need

442

not conflict with what clinicians would have chosen for them just because they are the parents’

443

own: in one large controlled trial, a web-based MMR decision-aid and leaflet not only reduced

444

decisional uncertainty among parents—it increased MMR uptake when compared with non-

445

intervention (Shourie et al. 2015). Whatever the support provided, direct reference to herd

446

immunity (versus, say, ‘community immunity’) may undermine acceptance: the term ‘herd’ can

447

suggest that vaccinating entails a “herd mentality.”

448

4.2 Leveraging Values

449

Recall that some parents saw herd immunity as a doubtful construct anyhow because others

450

might not vaccinate their children. Other parents’ unreliability meant that depending on herd

451

immunity (i.e., on others) to protect one’s own children was unwise. In addition, it would entail

452

shirking one’s parental responsibility to safeguard child health. Individual benefit came from

453

vaccinating—not from naively assuming that one could free-ride: the tragedy was not for the

454

commons but for one’s child.

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Parents avoiding vaccinations never presented themselves as witting beneficiaries playing

456

the system. They also seemed mostly unaware that others might suffer due to lowered herd

457

immunity. When they did consider that other children might fall ill (or when reminded by the

458

prompt to do so), they read such infections through a neoliberal individualist lens, ascribing them

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459

to parental laxity (e.g., failure to build one’s children’s immune systems through healthful

460

living). In keeping also with (gendered) expectations that tie caregiving to the domestic realm,

461

the parent’s (i.e., mother’s) obligation was clearly to home, not herd. Following advertising’s social marketing paradigm, parent distaste for the idea of

463

depending on others and preference for being independent of herd in/activity might thus serve as

464

a cultural lever for pro-vaccine outreach. Like birth control messaging for women that

465

stereotypes men as unreliable (Campo-Engelstein, 2013), vaccine messaging might frame free-

466

riding—doing nothing—as foolhardy compared to taking independent responsibility for one’s

467

child’s health, and as shameful compared to proactively fulfilling parental role obligations

468

(evoking shame while ‘nudging’ people toward expert-desired behavior can be ethically

469

problematic, such as when addictive behaviors like smoking are targeted, but shame has proven a

470

valuable public health tool; see Eyal 2014; regarding vaccine messaging ethics more broadly, see

471

Hendrix et al. 2016). Upward-trending PBE rates could be referenced to reinforce the message

472

that taking independent responsiblity is necessary (rather than to erroneously suggest, even

473

inadvertently, as per Kahan (2013), that vaccine hesitance is the norm). This approach, which

474

provides parents a reason to keep vaccinating given the low incidence of VPDs today, might be

475

particularly suited to the undecided (‘fence sitters’; Leask, 2011). Effectiveness could be tested

476

following Hershey and colleagues (1994), who were among the first to establish quantitatively

477

that vaccine message framing can significantly alter intent to vaccinate.

478

4.3 Social Ties

479

Letting go of herd immunity messaging is another option. In the research just mentioned,

480

Hershey and colleagues noted that frames highlighting the collective good only can work to

481

promote vaccine uptake if “individuals in groups have strong social ties” (1994: 186). My

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findings suggest that perceived ties to the broader collective—public health’s ‘herd’—are weak

483

among today’s selective vaccinators, at least in the US context. For instance, parents said they

484

could not count on others to hold up their end of the social contract regarding vaccination.

485

Indeed, as Putnam (2000) has argued with reference to myriad forms of civic engagement, social

486

connectedness has declined among US citizens. Putnam, who used bowling leagues as his

487

exemplar, did overlook newer forms of connectivity, such as though social media; but as Juris

488

(2012) has shown, connections thus built are actually quite fragile, and incommensurate.

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482

Juris’s conclusions resonate with Andersen and colleagues’ distinction between nominal

490

and active association memberships. Taking such into account, Andersen and colleagues (2006)

491

documented a clear decline in association activity among Americans. Further, when they

492

explored gender, which Putnam had not, they found that this decline was concentrated among

493

women, whose free time had shrunk and parental responsibilities risen relative to men’s. This

494

finding is particularly significant in the context of vaccine decision-making—generally the

495

purview of mothers.

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It also is significant that there was no gendered pattern in the comparison nations,

497

Canada, the Netherlands, and the UK, where families are smaller and state support for childcare

498

and early childhood education is higher than in the US (Andersen, Curtis, & Grabb, 2006: 397).

499

Concurrently, pediatric vaccination rates are higher in the UK and Netherlands (UNICEF Office

500

of Research, 2013: 14); in Canada they are not—but this has been attributed to regulatory and

501

reporting issues (Scheifele, Halperin, & Bettinger, 2014).

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The rise in individualism and fall in collectivism seen in the USA more than elsewhere

503

has occurred not just in tandem with decreased support for mothering, itself a more intensive job

504

now (Reich, 2014; and see Faircloth, 2010). It also is concurrent with the emergence of an

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individual rights-based ethic and the ascendance of a superficial discourse of ‘tolerance’ that

506

leaves little room for the kind of empathy necessary to feel strongly that ‘I am my brother’s

507

keeper’ (Twenge, Carter, & Campbell, 2015). Given the situation, shifts in family and social

508

policy following, for instance, the Netherlands model may do far more than clever messaging to

509

affect vaccine uptake.

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Right now, however, parent decisions are based more on concerns for their own children

511

than for the health of the herd. My findings in this regard resonate with Hendrix and colleagues’

512

large, survey-based test of whether telling parents of vaccination’s social benefits increased their

513

intent to vaccinate: it did not—except when benefits to their children also were mentioned

514

(Hendrix et al., 2014). The present project not only corroborates this finding; it provides a rich

515

description of why, links parental viewpoints to prominent cultural values, and offers details

516

(such as regarding the perceived irresponsibility of other parents, and adult immunity) that might

517

be leveraged non-coercively to affect vaccine decisions.

518

4.3 Limitations

519

Despite participant exposure to mass media and national conversations regarding vaccination,

520

findings may be regionally specific. Also, the research relied upon retrospective data, and used a

521

rapid assessment technique to collect the narrative data. Although my prior experience with a

522

community where vaccine hesitancy is the overt norm (Sobo, 2015) allowed me to optimize

523

interview data, as did triangulation with other forms of data collected, more questions might have

524

revealed a more nuanced picture. Nonetheless, the protocol’s brevity enabled data collection

525

from busy parents who otherwise would not have participated.

526

5. Conclusion

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Findings confirmed that simplistic vaccine-related messaging regarding ‘herd immunity’ is

528

unnecessary and unheeded. Parents who were unfamiliar with public health’s conceptualization

529

of herd immunity generally vaccinated anyhow. They did so not for the good of others but for the

530

good of their individual children. A unique study finding was that vaccinating parents often feel

531

that others cannot be counted on to immunize and to thereby uphold herd immunity.

532

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527

Another novel finding was that parents with ‘correct’ understandings often decide not to conform to pediatric vaccine recommendations due to concurrently held understandings.

534

Knowledge regarding adult immunity levels and other aspects of herd immunity not addressed in

535

present public health campaigns lead many to see herd immunity as unnecessary, unproven,

536

illogical, unrealistic, and unreliable. In this, herd immunity is anything but irrelevant.

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Given the high interest in self-education found among selective vaccinators, sensitive provision, to such parents, of information speaking in relative detail to aspects of herd immunity

539

that were questioned (e.g., as shown in Table 4) may be very welcomed. Additionally, messaging

540

might leverage the pervasive view that a ‘good’ parent should not, and cannot, count on the

541

collective. Given the state of civic engagement in the USA today, which is particularly low

542

amongst women, and short of changes in family and social policy that might make mothering a

543

less intensive job, such messaging may be one of the few ways that the presently low risk US

544

children have for contracting VPDs can be voluntarily maintained.

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Table 1. Sample Characteristics (N=53) Non-vaccinators

Partial

Full (up-to-date)

participants

(n=7)

(selective)

vaccinators

vaccinators

(n=33)

(N=53)

RI PT

All

years) Number of Children

35

37

36

34

(SD=6)

(SD=10)

(SD=5)

(SD=6)

1.3

1.4

1.2

1.3

(SD=.46)

(average) Income (average)

$104,063

(SD=.54)

(SD=.38)

(SD=.54)

$99,571

$115,900

$100,844

(SD= $39,153)

(SD=$86,019

(SD=$56,979)

TE D

(SD=$63,161)

M AN U

Age (average,

SC

(n=13)

34 White

5 White

10 White

19 White

reported)

4 Filipina

1 Filipina

1 Filipina

2 Filipina

6 Latina

1 Unstated

1 Latina

5 Latina

1 Asian

2 Asian

EP

Ethnicity (self-

3 Asian

AC C

545

Postgraduate

1 Native

1 Native

American

American

1 Black

1 Black

4 Unstated

3 Unstated

25/53

2/7

24

6/13

17/33

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education (proportion with a Master’s degree

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*All had completed high school.

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or more)*

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Table 2. ‘Correct’ Knowledge of Herd Immunity (N=53) All parents

Non-

Partial (selective)

Full (up-to-date)

Knowledge

(N=53)a

vaccinators

vaccinators (n=13)

vaccinators (n=33)

(n=7)a

Level 16 (30.2%)

1

2

In name only

12 (22.6%)

5

2

Total (None +

28 (52.8)

6 (85.7%)

In name only) 15 (28.3%)

Delineatedc

9 (17.0%)

Total (General +

24 (45.3%)

Delineated)

4 (30.8%)

13 5

18 (54.5%)

0

5

10

0

4

5

0

9 (69.2%)

15 (45.5%)

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Generalb

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None

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‘Correct’

M AN U

547

a. One participant did not receive the prompt.

549

b. Understands that the more individuals are vaccinated for a given vaccine-preventable disease,

550

the lower one’s chances are of contracting that disease. May or may not know the term ‘herd

551

immunity.’

552

c. Refers to the mechanism underlying herd immunity and/or to classes of vulnerable individuals

553

who might benefit particularly from herd immunity.

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548

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554

Table 3. Tool for Real-time Assessment of Information Literacy Skills (TRAILS) 12th grade

555

‘Evaluate Sources and Information’ component scores by index child’s vaccination status Non-vaccinators

Partial or

Full or up-to-

participants

(n=7)

selective

date vaccinators

vaccinators

(n=33)

(N=53)

RI PT

All

(n=13) 70.94

60.00

76.15

SC

Score (average)a

71.21

a. TRAILS does not offer benchmark data for this component only but, nationally, the average

557

general TRAILS assessment score is 51.9% (see Kent State University Libraries, 2014)

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556

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Table 4. Herd Immunity: Emergent Themes and Example Quotations Domain

Definition

Example Quotation

Protecting others (particularly

“It may help to protect some other people who

the vulnerable) via herd

have weakened immune systems” [Lisa;

immunity is a social good

selective vaccinator]

SC

Social Good

RI PT

POSITIVE THEMES

generally Herd immunity minimizes

“The more kids that are vaccinated the less

contagion and thus thwarts

chance there is of an outbreak of measles or

epidemic outbreaks; or herd

some other disease” [Ashley; full vaccinator]

immunity leads to the

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eradication of disease

M AN U

Preventive

I do not want my child to be a

“I don’t want to be the one who’s gonna end up

Citizen

source of contagion

having [my child] get the whole classroom sick”

EP

Good

[Alexis selective vaccinator]

NEUTRAL THEMES

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Ancillary

Protecting my own child from “It was mostly for him, but I think it’s kind of a disease is my highest priority;

social responsibility” [Jane; full vaccinator]

herd immunity is an ancillary benefit

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Because one must take self-

“If you let your immune system get run down,

responsibility for one’s

you will get sick… so I don’t really concern

child’s health, herd immunity

myself with what’s going on in the community”

is a non-issue

[Brooke; non-vaccinator]

RI PT

Irrelevant

NEGATIVE THEMES

Unproven

“Maybe if we had rampant diseases that we were

eradicated anyhow, so mass

vaccinating against I would think about that”

vaccination is unnecessary

[Emily; selective vaccinator]

Diseases come and go in cycles anyhow and herd

SC

Diseases have been mostly

M AN U

Unnecessary

“In the research that I’ve done, you see that diseases come and go over periods of time… People attribute the disappearance of these

waning cases does not prove

diseases or the prevalence of them to herd

causality

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immunity’s correlation with

immunity but I don’t know that that’s really scientifically sound because diseases kind of

Herd immunity is an illogical

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Illogical

EP

come in trends” [Erin; selective vaccinator]

proposition, because vaccines

“If you’re vaccinated you can also be a carrier” [Elizabeth, non-vaccinator]

don’t always work

Unrealistic

Herd immunity’s mechanism

“As adults we don’t get boosters…most of the

makes sense but herd

adults walking around in this world are not

immunity cannot be achieved

actually immune” [Joyelyn; selective vaccinator]

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because immunity wanes over time and adults do not get

The community cannot be

“I don’t want to depend on herd immunity to

counted on to vaccinate

protect him from these diseases. So I don’t trust

(focus is on others as slackers

the other parents I guess” [Allison; full

whereas focus for ‘Irrelevant’

vaccinator]

Exploitable

Some people do not get

M AN U

is on self)

SC

Unreliable

RI PT

(re)vaccinated

“People who are anti-vaccine think that if most

vaccinated when everyone

kids are [vaccinated] that the presence of the

else is vaccinated

vaccinated kid will protect others against

The term ‘herd’ is opposite to

“A lot of people just make blind—they follow

individualism or free choice

because they’re told ‘oh we’re gonna do this’

and implies a herd mentality

and they just do it… I want to make my own

Self-

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Demeaning

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disease” [Shannon; full vaccinator]

perpetuating

decisions” [Ana; selective vaccinator]

Herd immunity means that

“It’s almost like the herd immunity becomes a

most children are not exposed

negative… because now I will, probably will go

to diseases naturally, which in ahead and get that because I want him to be turn makes vaccination

protected when, you now from chicken pox

necessary

when he’s older… when it can be dangerous”

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[Angela; selective vaccinator]

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560

REFERENCES CITED:

561

Aliferis, L., 2016. Why Vaccination Rates Are Up Across California. State of Health, KQED News (January 20th) . Retrieved from http://ww2.kqed.org/stateofhealth/2016/01/20/why-

563

vaccination-rates-are-up-across-california/.

565 566

Amanna, I. J., Carlson, N. E., & Slifka, M. K., 2007. Duration of Humoral Immunity to Common Viral and Vaccine Antigens. New Engl. J. Med. 357 (19), 1903-1915.

Andersen, R., Curtis, J., & Grabb, E., 2006. Trends in civic association activity in four

SC

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RI PT

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