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Influenza vaccination rates in Ontario children: Implications for universal childhood vaccination policy
Vaccine 27 (2009) 2350–2355
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Influenza vaccination rates in Ontario children: Implications for universal childhood vaccination policy Kathy Moran a,∗ , Sarah Maaten b , Astrid Guttmann b,c,d , David Northrup e , Jeffrey C. Kwong b,f a
Durham Region Health Department and York Region Community and Health Services, Public Health Branch, Ontario, Canada Institute for Clinical Evaluative Sciences (ICES), Toronto, Canada Division of Paediatric Medicine, The Hospital for Sick Children, Canada d Departments of Paediatrics and Health Policy, Management and Evaluation, University of Toronto, Canada e Institute for Social Research, York University, Toronto, Canada f Department of Family and Community Medicine and Dalla Lana School of Public Health, University of Toronto, Canada b c
a r t i c l e
i n f o
Article history: Received 4 November 2008 Received in revised form 30 January 2009 Accepted 5 February 2009 Available online 13 February 2009 Keywords: Influenza Universal vaccination Vaccination rates
a b s t r a c t The aims of this study were to estimate influenza vaccination coverage for children during the 2006–2007 influenza season in Ontario, Canada, where universal vaccination is available, and to compare the rate among children aged 6–23 months with corresponding rates from other Canadian provinces that specifically target this high-risk group. We conducted a telephone survey of caregivers of children aged 6 months–11 years that included 4854 children from 3029 households. Ontario’s vaccination rate (complete and partial coverage combined) for children aged 2–11 years was 28.3% (95% CI 26.3–30.5%) for healthy children and 36.8% (95% CI 31.4–42.5%) for those with chronic conditions. Immunization coverage of children aged 6–23 months was 24.0% (95% CI 20.6–27.7%) in Ontario, similar to Manitoba’s rate of 24.1% but lower than rates in other provinces: Nova Scotia (35.5%), Quebec (41.8% for 1 year olds and 37.7% for 2 year olds during the 2005–2006 season), Saskatchewan (32.5%) and Alberta (52.2%). Universal vaccination in Ontario has achieved modest coverage in children aged 2–11 years, but has been less successful than targeted programs in vaccinating infants aged 6–23 months. Crown Copyright © 2009 Published by Elsevier Ltd. All rights reserved.
1. Introduction In 2000, a universal influenza immunization program (UIIP) offering free vaccination to all residents aged 6 months or older was introduced in Ontario, Canada’s largest province with a population of 12 million [1]. This program delivers influenza vaccines through a variety of settings, including physician offices, workplaces, community- and school-based clinics, and pharmacies, and uses extensive media campaigns to promote awareness of the availability and benefits of influenza vaccination. Over the same time period, other provinces maintained targeted influenza programs offering free vaccination only to identified high-risk groups, including children with certain chronic medical conditions [2]. By 2003, based on a growing body of evidence that young children suffer a considerable burden of illness related to influenza, both the U.S. Advisory Committee on Immunization Practices (ACIP)
∗ Corresponding author at: Epidemiology and Research, York Region Community and Health Services Department, Public Health Branch, 17250 Yonge Street, Newmarket, ON, L3Y 6Z1 Canada. Tel.: +1 905 830 4444x4507; fax: +1 905 895 3166. E-mail address: [email protected] (K. Moran).
and Canada’s National Advisory Committee on Immunizations recommended annual influenza immunization for all healthy children aged 6–23 months [3,4]. Austria and Finland are the only European countries to have introduced similar programs [5,6]. ACIP has since expanded their recommendation to include children aged 24–59 months [7], and more recently, children aged 5–19 years [8], whereas these expanded recommendations were not adopted in Canada. The introduction of Ontario’s UIIP has been associated with greater increases in vaccine uptake in the Ontario population aged 12 years or older compared with increases in other provinces [9,10]. This incremental effect extended to high-risk groups such as those with chronic conditions, even though they were already covered under targeted programs. However, in contrast to other jurisdictions that have assessed influenza vaccination rates in children, coverage rates for Ontario children under 12 years of age have never been measured. Therefore, we sought to estimate influenza vaccination coverage rates in Ontario children less than 12 years of age for the 2006–2007 influenza season and to describe reasons for nonimmunization. A secondary objective was to compare Ontario rates for children aged 6–23 months with estimates from other provinces to determine the effectiveness of a universal program for reaching children in this high-risk age group.
0264-410X/$ – see front matter. Crown Copyright © 2009 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.vaccine.2009.02.017
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2. Materials and methods
2.3. Vaccination rate estimates from other provinces
2.1. Study population and setting
Estimates of vaccination coverage among children aged 6–23 months were obtained from other provinces, where available. Vaccination coverage rates from Manitoba [11], Saskatchewan [12], and Alberta were obtained from immunization registries. Immunization data were captured through a combination of physician billing claims and public health reporting (paper- and web-based formats). Nova Scotia also used a combination of physician billing data and aggregated public health vaccination delivery data [13]. Provincial coverage rates from these four provinces were calculated using varying denominator definitions. In addition, extracting the appropriate number of doses was not possible hence only combined rates (complete and partial coverage) are reported. Quebec conducted a mail-based survey, estimating complete and partial coverage rates in two cohorts of children: aged 14–17 months and aged 24–27 months [14].
In 2006, Ontario had an estimated population of over 12,600,000 of which 14% were children 11 years of age or younger. All Ontarians are eligible for universally accessible, publicly funded health care services, including immunizations. For children, most influenza immunizations are delivered in physician offices or in communityor school-based clinics that are administered by public health units [Unpublished data, Public Health Division, Ontario Ministry of Health and Long-Term Care]. There is no provincially coordinated system to monitor influenza vaccine uptake. Ethics approvals were obtained from the Sunnybrook Health Sciences Centre Research Ethics Board, York University’s Human Participants Review Subcommittee, Durham Region Health Department’s Scientific and Ethical Review Committee, the University of Manitoba Research Ethics Board, and the Health Information Privacy Committee of Manitoba Health and Healthy Living. 2.2. Data collection and definitions From April 14 to September 2, 2007, a telephone survey of English-speaking Ontario households was conducted. Households were sampled using random digit dialing. Households were initially screened for the presence of children and then the person most responsible for caring for the children (PMR) was identified. Proxy information was collected on all children in the household who were 6 months–11 years old, as of September 30, 2006. Information collected from the PMR included each child’s age, sex, current influenza vaccination status, prior vaccination history, reason for receiving or not receiving influenza vaccination, location where the vaccination was given and the presence of selected chronic conditions. Household information included household size and the highest educational attainment of the PMR. The PMR was identified by asking “What is your relationship to the children in this household?” Vaccination coverage for the 2006–2007 season was derived from the PMR’s response to the question, “Since September 2006, has [child] received a flu shot?” Prior vaccination history was determined by asking the PMR: “Prior to September 2006, did [child] ever have a flu shot?” For all children aged 6–23 months and for children aged 2–8 years with no prior vaccination history, the PMR was asked: “Did [child] receive two flu shots since September 2006?” Complete and partial coverage were defined according to Canadian guidelines for influenza vaccination of children [2]. Children younger than 9 years require two lifetime doses to be considered completely immunized, whereas children 9 years or older require only one dose. In our survey, children under the age of 9 years who had received only one lifetime dose were considered partially immunized. The presence of chronic conditions for which influenza vaccination is specifically recommended was determined by asking the PMR if “a doctor, nurse or other health professional ever said that [child] had any of the following conditions: lung problems associated with prematurity, diabetes, sickle cell anemia, weakened immune system, or currently has asthma, or lung, heart or kidney problems, or a chronic health problem treated by taking aspirin every day” [2]. High-risk groups were defined as children aged 6–23 months and children aged 2–11 years with chronic conditions. The reason for receiving or not receiving influenza vaccination was identified by asking the PMR for the “main reason”. Only one response was accepted. If multiple responses were given, the PMR was prompted for the most important reason.
2.4. Statistical analysis The unit of analysis was the individual child. Cross-tabulations were used to determine influenza vaccination coverage in healthy children aged 2–11 years and in the two high-risk groups. Frequencies were used to determine reasons for receiving or not receiving influenza vaccination, and the location where the vaccination was given. All data were analyzed accounting for household clustering and stratified by public health unit. Survey data were age- and sex-adjusted using the 2006 Ontario population estimates. 3. Results The sample included 4980 children from 3029 households. If the PMR was unable to answer questions related to current influenza vaccination status (n = 122) and age (n = 4), the child was excluded. The final study sample was 4854. The response rate, calculated using a standard definition which estimates what proportion of cases of unknown eligibility is actually eligible, was 70.2% [15]. The total number of households screened was 29,096 and an estimated 10% of households had at least one child aged 6 months–11 years. A small number of eligible households (n = 117) refused to participate. Households were initially screened for the presence of children followed by the selection of the PMR. As the PMR was not randomly selected, the profile of the PMR is not representative of Ontario’s adult population. The mean age of the PMR was 37 years (range 18–82). The PMR was most frequently the parent (98.0%, 95% CI 97.3–98.5%), female (73.8%, 95% CI 71.8–75.8%), and in a married or common law union (89.3%, 95% CI 87.9–90.5%). The mean household size was four persons (95% CI 4.3–4.4,range 2–13) and the mean number of children aged 6 months–11 years in each household was two (95% CI 1.9–2.0, range 1–7). Table 1 further describes the characteristics of the sample population. In Ontario, the influenza vaccination coverage rate for complete immunization was 22.0% (95% CI 20.2–24.0%) in healthy children aged 2–11 years old (Table 2). For the high-risk groups, the complete coverage rate in children aged 2–11 years with chronic medical conditions was higher at 30.8% (95% CI 25.8–36.3%) but lower in children aged 6–23 months at 10.2% (95% CI 7.9–13.0%). Ontario’s rate for complete coverage in children aged 6–23 months was lower than rates in Quebec (33.3% for 1 year olds and 33.6% for 2 year olds during the 2005–2006 season). The combined coverage rate in Ontario children aged 6–23 months (24.9%, 95% CI 20.6–27.7%) was similar to Manitoba’s combined rate of 24.1%, however it was lower than combined rates in Nova Scotia (35.5%), Quebec (41.8% for 1 year olds and 37.7% for 2
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Table 1 Selected characteristics of the sample populationa . Total (n) un-weighted
%Weighted
95% CI
%Ontario
Sex of child Male Female
2488 2356
50.7 49.3
49.0–52.3 47.7–51.0
51.1 48.9
Age of childb 6–23 months 2–11 years
800 4054
16.9 83.1
15.7–18.1 81.9–84.3
11.4 88.1
Prevalence of chronic conditions (2–11 years) Present Absent
465 3681
10.7 89.3
9.7–11.9 88.1–90.3
*
Educational attainment of respondentc Less than high school High school + College/university
276 1170 3387
4.6 22.7 72.7
3.8–5.7 20.9–24.6 70.7–74.6
13.6 33.8 52.7
Home language of respondentc English French Non-official languages Otherd
4,159 110 433 143
81.8 2.2 12.2 3.9
80.0–83.5 1.6–2.8 10.7–13.7 3.1–4.9
80.3 2.4 15.1 2.2
b
a Excludes missing age (n = 4) and ‘don’t know’ responses to “Since September 2006, has [child] received a flu shot?” (n = 122). Excludes item non-response (‘don’t know’ and ‘refused’ responses) for each characteristic. b Ontario comparison from the Ontario Population Estimates, 2006, Provincial Health Planning Database, Health Planning Branch, Ontario Ministry of Health and Long-Term Care. c Ontario comparison from the 2006 Census, Statistics Canada (topic-based tabulation). For education, aged 25–64 years only. d Includes not specified responses and multiple responses. * No Ontario comparison. Asthma prevalence estimated at 12.3% in children aged 0–4 years, 10.0% in children aged 5–9 years and 7.0% in children aged 10–14 years [30].
Table 2 Influenza immunization coverage in Ontario childrena . %Complete/Partial combined (95% CIb )
%Complete (95% CIb )
%Partialc (95% CIb )
6–23 months
##
Ontario Nova Scotia* Quebec** Quebec*** Manitoba# Saskatchewan# Alberta#
24.0 (20.6–27.7) 35.5 41.8 37.7 24.1 32.5 52.2
10.2 (7.9–13.0) na 33.3 (28.8-37.9) 33.6 (29.0-39.4) na na na
13.8 (11.2–16.8) na 8.5 4.1 na na na
2–11 years with chronic conditions 2–11 years without chronic conditions
Ontario## Ontario##
36.8 (31.4–42.5) 28.3 (26.3–30.5)
30.8 (25.8–36.3) 22.0 (20.2–24.0)
6.0d (3.5–9.9) 6.3 (5.4–7.5)
Risk group
Province
a
Excludes missing age (n = 4) and ‘don’t know’ responses to “Since September 2006, has [child] received a flu shot?” (n = 122). Confidence intervals calculated for Ontario’s survey data only and reported for Quebec results, where available. c Received only 1 dose when 2 doses were indicated for the child according to Canadian guidelines. d Caution due to high sampling variability. * Based on physician billing claims and aggregated vaccine delivery data. ** Based on parental-reporting via mail survey, 2005–2006 season: <18 months. *** Based on parental-reporting via mail survey, 2005–2006 season: ≥18 months. # Based on immunization registry data using physician billing claims and public health reporting. ## Based on parental-reporting via mail survey. na data not available. b
year olds during the 2005–2006 season), Saskatchewan (32.5%) and Alberta (52.2%) (Table 2). Fig. 1 identifies where influenza vaccinations were given. The majority of vaccinations were reportedly given in physician offices or medical clinics (76.5%, 95% CI 73.3–79.5%), confirming unpublished data from the Ontario Ministry of Health and Long-Term Care. Children aged 6–23 months received their vaccinations more often in physician offices; 82.2% (95% CI 72.9–88.9%) compared to 77.9% (95% CI 69.6–83.9%) and 74.0% (95% CI 70.2–77.5%) in children aged 2–11 years with chronic medical conditions and healthy children aged 2–11 years old, respectively (p < 0.05). The most frequently reported reason for receiving influenza vaccination was health-related, which accounted for three-quarters of all responses. Over half (53.6%) reported that their children were vaccinated to avoid getting influenza. Fourteen percent (14.1%) reported non-specific health reasons while 5.7% reported that their child was ‘at risk’. Other than for health reasons, the most frequently
Fig. 1. Where Ontario children receive influenza vaccinationsa .
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Table 3 Most important reason for receiving influenza vaccination* . Reason
%Total
95% CI
6–23 months (%)
Health: avoid getting influenza Health: at risk Health: avoid infecting others Health: general Recommended: by health professional Recommended: by other Out of habit Easy access/convenient Other***
53.6
49.9–57.3
50.6
4.4–7.4 1.7–4.1
NR NR
11.7–17.0 7.9–12.5
14.2** 19.7**
2.1–4.7 3.3–6.5 1.7–3.8 2.6–5.2
NR NR NR NR
5.7 2.6** 14.1 10.0 3.1** 4.6** 2.6** 3.7**
95% CI 42.2–59.0
2–11 years with chronic conditions (%) 47.1
95% CI 39.5–54.9
NR NR 9.2–21.3 13.8–27.3
2–11 years without chronic conditions (%) 55.7
95% CI 51.4–60.0
NR NR
10.9** 8.1**
6.9–16.6 4.7–13.6
NR NR NR NR
14.9 8.4
12.1–18.3 6.2–11.2
NR NR NR NR
n = 1467. * Includes complete/partial coverage, i.e., received at least 1 dose; response was the most important reason, single response only accepted. ** Caution due to high sampling variability. *** Includes ‘don’t know’ responses. NR not releasable; unreliable estimates in one or more risk groups. Table 4 Most important reason for not receiving influenza vaccination* . Reason
%Total
95% CI
6–23 months (%)
95% CI
2–11 years with chronic conditions (%)
95% CI
2–11 years without chronic conditions (%)
95% CI
Need: not needed in general Need: child does not need Need: doctor did not recommend Need: other Concern: vaccine safety Concern: will cause influenza Concern: does not work Access: inconvenient/hard to find Fear of needles Other***
32.2 20.9 5.3 1.8** 9.6 1.3** 4.1 7.7 2.0** 15.0
29.9–34.7 18.9–23.0 4.3–6.6 1.3–2.5 8.2–11.1 0.9–2.0 3.2–5.4 6.5–9.1 1.4–2.7 13.4–16.8
28.4 29.8 9.9 NR 4.5** NR NR 5.5** NR 15.1
24.4–32.9 25.7–34.3 7.5–13.0
28.8 13.3 3.6** NR 17.3 NR NR 8.9** NR 17.6
24.1–34.0 10.0–17.4 2.0–6.2
33.9 20.1 4.5 NR 9.3 NR NR 8.1 NR 14.5
31.1–36.8 17.8–22.6 3.4–5.9
3.0–6.7
3.8–8.0 12.1–18.7
13.6–21.8
6.3–12.5 13.7–22.3
7.8–11.1
6.6–9.8 12.6–16.6
n = 3387. * Includes complete/partial coverage, i.e., received at least 1 dose; response was the most important reason, single response only accepted. ** Caution due to high sampling variability. *** Includes ‘don’t know’ responses. NR not releasable; unreliable estimates in one or more risk groups.
reported reason for influenza vaccination was a recommendation (13.1%), most often by a health professional. The most important reason for receiving influenza vaccination differed by risk group. A recommendation from a health professional was reported more often in the youngest age group at 19.7% for children aged 6–23 months (Table 3). For those who chose not to vaccinate their children in the 2006–2007 influenza season, one-third (32.2%) made a general overall comment that influenza vaccination was not needed, while a further 20.9% specifically identified that their child did not need to be vaccinated (Table 4). Almost 10% (9.6%) expressed concern about vaccine safety and a further 7.7% reported barriers to access. Five percent (5.3%) reported that vaccination was not recommended. A small percentage (4.1%) expressed concerns regarding vaccine effectiveness. Differences by risk group were also observed. Respondents with children aged 6–23 months more frequently reported that their child did not need vaccination (29.8%) or vaccination was not recommended by their doctor (9.9%). 4. Discussion This is the first population estimate of influenza vaccination coverage rates in Ontario children since the introduction of universal vaccination in 2000. Vaccination rates among high-risk children during the 2006–2007 influenza season were well below the national target of 70% [16], and for 6–23 month olds, below rates in most other Canadian provinces that target this age group.
This study was conducted in the seventh season of universal coverage in Ontario. Low vaccination coverage due to poor public awareness would seem unlikely and the majority of respondents who chose to vaccinate their children cited reasons that enhanced health, including those who specifically identified illness prevention (most frequently reported reason) or prevention of transmission. However, increasing public knowledge about the serious health risks associated with influenza and the benefits of vaccines is clearly needed [17–22]. For respondents who chose not to vaccinate their children, the most common reason related to beliefs about the lack of need for vaccination, particularly for children aged 6–23 months. In addition to ongoing public education efforts, a recommendation from a health professional is a key component to improving vaccination coverage [20–23]. This was the third most frequently reported reason among all respondents who chose to vaccinate their children and ranked second among respondents with children aged 6–23 months. For those who chose not to vaccinate their children, particularly for respondents with children aged 6–23 months, over half questioned the need for vaccination. Clear and consistent messaging regarding the risks and benefits of immunizations, including vaccine safety, is important for increasing coverage rates, and health professionals play an essential role in changing public perception [17–23]. Influenza vaccines for children are safe, but the evidence of vaccine efficacy for those aged 6–23 months is more limited [24]. Some health care professionals may have reservations about recommending routine vaccination against influenza in these
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young children, despite good evidence of the substantial burden of illness in this age group [17]. In the context of a universal vaccination program, access issues were higher than expected. This reason, which included responses such as ‘inconvenient’ and ‘too busy’, may reflect less frequent physician visits in older children. This underscores the need to capitalize on all opportunities to promote influenza vaccination and to continue to provide a variety of delivery venues. The low rate in Ontario children aged 6–23 months compared to other jurisdictions with targeted programs was unexpected. Although the type of coverage data available varies by province, and comparisons are challenging due to a lack of standardization in data collection methodology and reporting definitions, we do not believe this would account for all of the observed variation. Parental knowledge, attitudes and beliefs play a key role in determining whether their children are vaccinated [20–23]. However, physician or other health professional recommendations are also important [18,20–22]. Across Canadian provinces, there is great variation in the proportion of routine childhood immunizations given by physicians versus public health nurses. Ontario and Manitoba have the highest proportion of immunizations given by physicians (personal communication, Anna-Maria Frescura, Public Health Agency of Canada). It may be that there has been lower uptake of the recommendations in this age group by physicians, possibly because the evidence suggesting that vaccine efficacy is lower in children under 2 years [24]. This study provides only a point estimate of coverage. Whether greater increases in children can be achieved under a universal program compared to targeted programs, as previously reported in Ontarians aged 12 years and older with and without chronic conditions [9,10], requires regular reporting to monitor trends. Surveys are a feasible and cost-effective method for repeatedly reporting on immunization status in the absence of a comprehensive registry [25], however parental-reported data has been shown to result in over-reporting of immunization status [23]. When collecting information on immunization status, prior immunization history or the prevalence of chronic conditions, there may have been a tendency for parents to respond in a manner that would have been viewed favorably. In addition, recall bias may have been important in the recollection of whether the child was immunized and the location where the vaccination was given as the survey was conducted over a 6-month period mostly after the end of influenza season. This may have resulted in parental confusion, particularly in older children who are more likely to receive influenza vaccination from different providers and at a variety of locations As with other survey research, this study has a number of other limitations. Almost three-quarters of respondents were university or college educated; much higher than expected in the general population. The coverage rate in this study likely over-estimates actual coverage as lower education attainment has been shown to negatively predict influenza and other vaccination in children [20,26]. Selection bias, which is not unique to survey research, cannot be ruled out as some households refused to participate while other eligible households may have chosen not to participate in the survey by reporting that they had no eligible children. Households without phone numbers, estimated at less than 2% [27], and households with only mobile telephones, estimated at 4% [28], were excluded. These households may differ from the study population and their impact on the study’s provincial coverage rates is unknown. In summary, influenza vaccine coverage rates in high-risk children across Canada are below national targets and funding universal access alone is unlikely to achieve these goals. Although the universal program in Ontario has achieved moderate rates of immunization overall, and higher rates in many high-risk populations compared to provinces with targeted programs, this is not the case for children aged 6–23 months. However, improving cov-
erage will require routinely available immunization data. Ontario is not amongst the Canadian provinces that have implemented population-based immunization registries. This lack of a registry has hindered efforts to provide ongoing monitoring of vaccine uptake, provide timely access to information to inform influenza vaccination planning and evaluation, and provide opportunities for health professionals to implement public health strategies to specifically target groups with low coverage [29], including children aged 6–23 months. Ensuring the success of a universal vaccination program must include the ability to assess coverage in all populations, especially those designated as high-risk. Acknowledgements We thank Charles Burchill and Wendy Au, Manitoba Centre for Health Policy, Rosalie Tuscherer, Saskatchewan Health, and Elaine Sartisan, Alberta Health and Wellness, for providing estimates of influenza vaccination coverage for children aged 6–23 months from their respective provinces. Contributions: Ms Moran had full access to all the Ontario survey data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Moran, Maaten, Guttmann, Northrup and Kwong. Acquisition of data: Northrup and Kwong. Analysis and interpretation of data: Moran, Maaten, Guttmann, Northrup and Kwong, Drafting of the manuscript: Moran and Kwong. Critical revision of the manuscript for important intellectual content: Moran, Maaten, Guttmann, Northrup and Kwong. Statistical analysis: Moran. Obtained funding: Moran, Guttmann and Kwong. Administrative, technical and material support: Moran, Maaten and Northrup. Study supervision: Moran and Kwong. Financial disclosure: Ms Moran and Maaten, Drs Kwong and Guttmann, and Mr. Northrup certify that all affiliations with or financial involvement, within the past 5 years and foreseeable future with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript of completed disclosed. Funding/support: This study was supported by the Canadian Institutes of Health Research (CIHR), Institute of Infection and Immunity, and Public Health Agency of Canada, Centre for Infectious Disease Prevention and Control, Research grant no. XIN 82408. Dr. Guttmann is supported in part by a CIHR New Investigator Award. Dr. Kwong was supported by a CIHR Fellowship Award at the time of the study and is currently supported by an Ontario MOHLTC Career Scientist Award and a University of Toronto, Department of Family and Community Medicine Research Scholar Award, and also receives some salary support from the ICES. This work was made possible with the support of ICES, which is funded in part by the Ontario MOHLTC. The opinions, results and conclusions are those of the authors, and no endorsement by the Ontario MOHLTC, ICES, or Manitoba Health and Healthy Living is intended or should be inferred. Role of the sponsor: Design and conduct: None. Collection, management, analysis and interpretation of the data: None. Preparation, review or approval of the manuscript: None. Additional contributions: None to report. References [1] Canada NewsWire. Ontario invests $38 million to ease emergency room pressures with universal vaccination program. http://ogov.newswire.ca/ontario/ GPOE/2000/07/25/c6018.html?lmatch=&lang=.html, 2000 July 25 [cited 2007 July 9];. [2] Public Health Agency of Canada. Canadian Immunization Guide. 7th ed. Ottawa: Her Majesty the Queen in Right of Canada; 2006. [3] National Advisory Committee on Immunization (NACI). Statement on influenza vaccination for the 2003–2004 season. Canada Communicable Disease Report 2003;29:1–20.
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[18] Humiston SG, Lerner EB, Hepworth E, Blythe T, Goepp JG. Parent opinions about universal influenza vaccination for infants and toddlers. Archives of Pediatrics & Adolescent Medicine 2005;159(February (2)):108–12. [19] Chobotuk TD, Kellner JD. Calgary based study of influenza vaccination for young children: parental beliefs and behaviours. Canada Communicable Disease Report 2006;32(July 1 (13)):141–50. [20] Daley MF, Crane LA, Chandramouli V, Beaty BL, Barrow J, Allred N, et al. Influenza among healthy young children: changes in parental attitudes and predictors of immunization during the 2003 to 2004 influenza season. Pediatrics 2006;117(February (2)):e268–77. [21] Nowalk MP, Lin CJ, Zimmerman RK, Ko FS, Hoberman A, Zoffel L, et al. Changes in parents’ perceptions of infant influenza vaccination over two years. Journal of the National Medical Association 2007;99(June (6)):636–41. [22] Grant VJ, Le Saux N, Plint AC, Correll R, Gaboury I, Ellis E, et al. Factors influencing childhood influenza immunization. Canadian Medical Association Journal 2003;168(January 7 (1)):39–41. [23] Nowalk MP, Zimmerman RK, Lin CJ, Ko FS, Raymund M, Hoberman A, et al. Parental perspectives on influenza immunization of children aged 6 to 23 months. American Journal of Preventive Medicine 2005;29(October (3)):210–4. [24] Jefferson T, Rivetti A, Harnden A, Di Pietrantonj C, Demicheli V. Vaccines for preventing influenza in healthy children. Cochrane Database of Systematic Reviews 2008;(2):Art. No.: CD004879. doi:10.1002/14651858.CD004879.pub3. [25] McWha L, MacArthur A, Badiani T, Schouten H, Tam T, King A. Measuring up: results from the National Immunization Coverage Survey, 2002. Canada Communicable Disease Report 2004;30(March 1 (5)):37–50. [26] Santibanez TA, Santoli JM, Bridges CB, Euler GL. Influenza vaccination coverage of children aged 6 to 23 months: the 2002–2003 and 2003–2004 influenza seasons. Pediatrics 2006;118(September (3)):1167–75. [27] Statistics Canada. Residential telephone service survey. Statistics Canada 2005, February 4. Available from: URL: http://www40.statcan. ca/l01/cst01/comm03b.htm. [28] Statistics Canada. Residential telephone service survey 2007. The Daily 2008, April 23. Available from: URL: http://www.statcan.ca/Daily/English/ 080423/d080423d.htm. [29] Canadian consensus conference on a national immunization records system. Canada Communicable Disease Report 1998, September 1;24(17):137–40. [30] To T, Gershon A, Guan J, Estrabillo E, Cicutto L. The burden of asthma in Ontario. ICES investigative report. Toronto: Institute for Clinical Evaluative Sciences; 2006.
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Influenza vaccination rates in Ontario children: Implications for universal childhood vaccination policy Kathy Moran a,∗ , Sarah Maaten b , Astrid Guttmann b,c,d , David Northrup e , Jeffrey C. Kwong b,f a
Durham Region Health Department and York Region Community and Health Services, Public Health Branch, Ontario, Canada Institute for Clinical Evaluative Sciences (ICES), Toronto, Canada Division of Paediatric Medicine, The Hospital for Sick Children, Canada d Departments of Paediatrics and Health Policy, Management and Evaluation, University of Toronto, Canada e Institute for Social Research, York University, Toronto, Canada f Department of Family and Community Medicine and Dalla Lana School of Public Health, University of Toronto, Canada b c
a r t i c l e
i n f o
Article history: Received 4 November 2008 Received in revised form 30 January 2009 Accepted 5 February 2009 Available online 13 February 2009 Keywords: Influenza Universal vaccination Vaccination rates
a b s t r a c t The aims of this study were to estimate influenza vaccination coverage for children during the 2006–2007 influenza season in Ontario, Canada, where universal vaccination is available, and to compare the rate among children aged 6–23 months with corresponding rates from other Canadian provinces that specifically target this high-risk group. We conducted a telephone survey of caregivers of children aged 6 months–11 years that included 4854 children from 3029 households. Ontario’s vaccination rate (complete and partial coverage combined) for children aged 2–11 years was 28.3% (95% CI 26.3–30.5%) for healthy children and 36.8% (95% CI 31.4–42.5%) for those with chronic conditions. Immunization coverage of children aged 6–23 months was 24.0% (95% CI 20.6–27.7%) in Ontario, similar to Manitoba’s rate of 24.1% but lower than rates in other provinces: Nova Scotia (35.5%), Quebec (41.8% for 1 year olds and 37.7% for 2 year olds during the 2005–2006 season), Saskatchewan (32.5%) and Alberta (52.2%). Universal vaccination in Ontario has achieved modest coverage in children aged 2–11 years, but has been less successful than targeted programs in vaccinating infants aged 6–23 months. Crown Copyright © 2009 Published by Elsevier Ltd. All rights reserved.
1. Introduction In 2000, a universal influenza immunization program (UIIP) offering free vaccination to all residents aged 6 months or older was introduced in Ontario, Canada’s largest province with a population of 12 million [1]. This program delivers influenza vaccines through a variety of settings, including physician offices, workplaces, community- and school-based clinics, and pharmacies, and uses extensive media campaigns to promote awareness of the availability and benefits of influenza vaccination. Over the same time period, other provinces maintained targeted influenza programs offering free vaccination only to identified high-risk groups, including children with certain chronic medical conditions [2]. By 2003, based on a growing body of evidence that young children suffer a considerable burden of illness related to influenza, both the U.S. Advisory Committee on Immunization Practices (ACIP)
∗ Corresponding author at: Epidemiology and Research, York Region Community and Health Services Department, Public Health Branch, 17250 Yonge Street, Newmarket, ON, L3Y 6Z1 Canada. Tel.: +1 905 830 4444x4507; fax: +1 905 895 3166. E-mail address: [email protected] (K. Moran).
and Canada’s National Advisory Committee on Immunizations recommended annual influenza immunization for all healthy children aged 6–23 months [3,4]. Austria and Finland are the only European countries to have introduced similar programs [5,6]. ACIP has since expanded their recommendation to include children aged 24–59 months [7], and more recently, children aged 5–19 years [8], whereas these expanded recommendations were not adopted in Canada. The introduction of Ontario’s UIIP has been associated with greater increases in vaccine uptake in the Ontario population aged 12 years or older compared with increases in other provinces [9,10]. This incremental effect extended to high-risk groups such as those with chronic conditions, even though they were already covered under targeted programs. However, in contrast to other jurisdictions that have assessed influenza vaccination rates in children, coverage rates for Ontario children under 12 years of age have never been measured. Therefore, we sought to estimate influenza vaccination coverage rates in Ontario children less than 12 years of age for the 2006–2007 influenza season and to describe reasons for nonimmunization. A secondary objective was to compare Ontario rates for children aged 6–23 months with estimates from other provinces to determine the effectiveness of a universal program for reaching children in this high-risk age group.
0264-410X/$ – see front matter. Crown Copyright © 2009 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.vaccine.2009.02.017
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2. Materials and methods
2.3. Vaccination rate estimates from other provinces
2.1. Study population and setting
Estimates of vaccination coverage among children aged 6–23 months were obtained from other provinces, where available. Vaccination coverage rates from Manitoba [11], Saskatchewan [12], and Alberta were obtained from immunization registries. Immunization data were captured through a combination of physician billing claims and public health reporting (paper- and web-based formats). Nova Scotia also used a combination of physician billing data and aggregated public health vaccination delivery data [13]. Provincial coverage rates from these four provinces were calculated using varying denominator definitions. In addition, extracting the appropriate number of doses was not possible hence only combined rates (complete and partial coverage) are reported. Quebec conducted a mail-based survey, estimating complete and partial coverage rates in two cohorts of children: aged 14–17 months and aged 24–27 months [14].
In 2006, Ontario had an estimated population of over 12,600,000 of which 14% were children 11 years of age or younger. All Ontarians are eligible for universally accessible, publicly funded health care services, including immunizations. For children, most influenza immunizations are delivered in physician offices or in communityor school-based clinics that are administered by public health units [Unpublished data, Public Health Division, Ontario Ministry of Health and Long-Term Care]. There is no provincially coordinated system to monitor influenza vaccine uptake. Ethics approvals were obtained from the Sunnybrook Health Sciences Centre Research Ethics Board, York University’s Human Participants Review Subcommittee, Durham Region Health Department’s Scientific and Ethical Review Committee, the University of Manitoba Research Ethics Board, and the Health Information Privacy Committee of Manitoba Health and Healthy Living. 2.2. Data collection and definitions From April 14 to September 2, 2007, a telephone survey of English-speaking Ontario households was conducted. Households were sampled using random digit dialing. Households were initially screened for the presence of children and then the person most responsible for caring for the children (PMR) was identified. Proxy information was collected on all children in the household who were 6 months–11 years old, as of September 30, 2006. Information collected from the PMR included each child’s age, sex, current influenza vaccination status, prior vaccination history, reason for receiving or not receiving influenza vaccination, location where the vaccination was given and the presence of selected chronic conditions. Household information included household size and the highest educational attainment of the PMR. The PMR was identified by asking “What is your relationship to the children in this household?” Vaccination coverage for the 2006–2007 season was derived from the PMR’s response to the question, “Since September 2006, has [child] received a flu shot?” Prior vaccination history was determined by asking the PMR: “Prior to September 2006, did [child] ever have a flu shot?” For all children aged 6–23 months and for children aged 2–8 years with no prior vaccination history, the PMR was asked: “Did [child] receive two flu shots since September 2006?” Complete and partial coverage were defined according to Canadian guidelines for influenza vaccination of children [2]. Children younger than 9 years require two lifetime doses to be considered completely immunized, whereas children 9 years or older require only one dose. In our survey, children under the age of 9 years who had received only one lifetime dose were considered partially immunized. The presence of chronic conditions for which influenza vaccination is specifically recommended was determined by asking the PMR if “a doctor, nurse or other health professional ever said that [child] had any of the following conditions: lung problems associated with prematurity, diabetes, sickle cell anemia, weakened immune system, or currently has asthma, or lung, heart or kidney problems, or a chronic health problem treated by taking aspirin every day” [2]. High-risk groups were defined as children aged 6–23 months and children aged 2–11 years with chronic conditions. The reason for receiving or not receiving influenza vaccination was identified by asking the PMR for the “main reason”. Only one response was accepted. If multiple responses were given, the PMR was prompted for the most important reason.
2.4. Statistical analysis The unit of analysis was the individual child. Cross-tabulations were used to determine influenza vaccination coverage in healthy children aged 2–11 years and in the two high-risk groups. Frequencies were used to determine reasons for receiving or not receiving influenza vaccination, and the location where the vaccination was given. All data were analyzed accounting for household clustering and stratified by public health unit. Survey data were age- and sex-adjusted using the 2006 Ontario population estimates. 3. Results The sample included 4980 children from 3029 households. If the PMR was unable to answer questions related to current influenza vaccination status (n = 122) and age (n = 4), the child was excluded. The final study sample was 4854. The response rate, calculated using a standard definition which estimates what proportion of cases of unknown eligibility is actually eligible, was 70.2% [15]. The total number of households screened was 29,096 and an estimated 10% of households had at least one child aged 6 months–11 years. A small number of eligible households (n = 117) refused to participate. Households were initially screened for the presence of children followed by the selection of the PMR. As the PMR was not randomly selected, the profile of the PMR is not representative of Ontario’s adult population. The mean age of the PMR was 37 years (range 18–82). The PMR was most frequently the parent (98.0%, 95% CI 97.3–98.5%), female (73.8%, 95% CI 71.8–75.8%), and in a married or common law union (89.3%, 95% CI 87.9–90.5%). The mean household size was four persons (95% CI 4.3–4.4,range 2–13) and the mean number of children aged 6 months–11 years in each household was two (95% CI 1.9–2.0, range 1–7). Table 1 further describes the characteristics of the sample population. In Ontario, the influenza vaccination coverage rate for complete immunization was 22.0% (95% CI 20.2–24.0%) in healthy children aged 2–11 years old (Table 2). For the high-risk groups, the complete coverage rate in children aged 2–11 years with chronic medical conditions was higher at 30.8% (95% CI 25.8–36.3%) but lower in children aged 6–23 months at 10.2% (95% CI 7.9–13.0%). Ontario’s rate for complete coverage in children aged 6–23 months was lower than rates in Quebec (33.3% for 1 year olds and 33.6% for 2 year olds during the 2005–2006 season). The combined coverage rate in Ontario children aged 6–23 months (24.9%, 95% CI 20.6–27.7%) was similar to Manitoba’s combined rate of 24.1%, however it was lower than combined rates in Nova Scotia (35.5%), Quebec (41.8% for 1 year olds and 37.7% for 2
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Table 1 Selected characteristics of the sample populationa . Total (n) un-weighted
%Weighted
95% CI
%Ontario
Sex of child Male Female
2488 2356
50.7 49.3
49.0–52.3 47.7–51.0
51.1 48.9
Age of childb 6–23 months 2–11 years
800 4054
16.9 83.1
15.7–18.1 81.9–84.3
11.4 88.1
Prevalence of chronic conditions (2–11 years) Present Absent
465 3681
10.7 89.3
9.7–11.9 88.1–90.3
*
Educational attainment of respondentc Less than high school High school + College/university
276 1170 3387
4.6 22.7 72.7
3.8–5.7 20.9–24.6 70.7–74.6
13.6 33.8 52.7
Home language of respondentc English French Non-official languages Otherd
4,159 110 433 143
81.8 2.2 12.2 3.9
80.0–83.5 1.6–2.8 10.7–13.7 3.1–4.9
80.3 2.4 15.1 2.2
b
a Excludes missing age (n = 4) and ‘don’t know’ responses to “Since September 2006, has [child] received a flu shot?” (n = 122). Excludes item non-response (‘don’t know’ and ‘refused’ responses) for each characteristic. b Ontario comparison from the Ontario Population Estimates, 2006, Provincial Health Planning Database, Health Planning Branch, Ontario Ministry of Health and Long-Term Care. c Ontario comparison from the 2006 Census, Statistics Canada (topic-based tabulation). For education, aged 25–64 years only. d Includes not specified responses and multiple responses. * No Ontario comparison. Asthma prevalence estimated at 12.3% in children aged 0–4 years, 10.0% in children aged 5–9 years and 7.0% in children aged 10–14 years [30].
Table 2 Influenza immunization coverage in Ontario childrena . %Complete/Partial combined (95% CIb )
%Complete (95% CIb )
%Partialc (95% CIb )
6–23 months
##
Ontario Nova Scotia* Quebec** Quebec*** Manitoba# Saskatchewan# Alberta#
24.0 (20.6–27.7) 35.5 41.8 37.7 24.1 32.5 52.2
10.2 (7.9–13.0) na 33.3 (28.8-37.9) 33.6 (29.0-39.4) na na na
13.8 (11.2–16.8) na 8.5 4.1 na na na
2–11 years with chronic conditions 2–11 years without chronic conditions
Ontario## Ontario##
36.8 (31.4–42.5) 28.3 (26.3–30.5)
30.8 (25.8–36.3) 22.0 (20.2–24.0)
6.0d (3.5–9.9) 6.3 (5.4–7.5)
Risk group
Province
a
Excludes missing age (n = 4) and ‘don’t know’ responses to “Since September 2006, has [child] received a flu shot?” (n = 122). Confidence intervals calculated for Ontario’s survey data only and reported for Quebec results, where available. c Received only 1 dose when 2 doses were indicated for the child according to Canadian guidelines. d Caution due to high sampling variability. * Based on physician billing claims and aggregated vaccine delivery data. ** Based on parental-reporting via mail survey, 2005–2006 season: <18 months. *** Based on parental-reporting via mail survey, 2005–2006 season: ≥18 months. # Based on immunization registry data using physician billing claims and public health reporting. ## Based on parental-reporting via mail survey. na data not available. b
year olds during the 2005–2006 season), Saskatchewan (32.5%) and Alberta (52.2%) (Table 2). Fig. 1 identifies where influenza vaccinations were given. The majority of vaccinations were reportedly given in physician offices or medical clinics (76.5%, 95% CI 73.3–79.5%), confirming unpublished data from the Ontario Ministry of Health and Long-Term Care. Children aged 6–23 months received their vaccinations more often in physician offices; 82.2% (95% CI 72.9–88.9%) compared to 77.9% (95% CI 69.6–83.9%) and 74.0% (95% CI 70.2–77.5%) in children aged 2–11 years with chronic medical conditions and healthy children aged 2–11 years old, respectively (p < 0.05). The most frequently reported reason for receiving influenza vaccination was health-related, which accounted for three-quarters of all responses. Over half (53.6%) reported that their children were vaccinated to avoid getting influenza. Fourteen percent (14.1%) reported non-specific health reasons while 5.7% reported that their child was ‘at risk’. Other than for health reasons, the most frequently
Fig. 1. Where Ontario children receive influenza vaccinationsa .
K. Moran et al. / Vaccine 27 (2009) 2350–2355
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Table 3 Most important reason for receiving influenza vaccination* . Reason
%Total
95% CI
6–23 months (%)
Health: avoid getting influenza Health: at risk Health: avoid infecting others Health: general Recommended: by health professional Recommended: by other Out of habit Easy access/convenient Other***
53.6
49.9–57.3
50.6
4.4–7.4 1.7–4.1
NR NR
11.7–17.0 7.9–12.5
14.2** 19.7**
2.1–4.7 3.3–6.5 1.7–3.8 2.6–5.2
NR NR NR NR
5.7 2.6** 14.1 10.0 3.1** 4.6** 2.6** 3.7**
95% CI 42.2–59.0
2–11 years with chronic conditions (%) 47.1
95% CI 39.5–54.9
NR NR 9.2–21.3 13.8–27.3
2–11 years without chronic conditions (%) 55.7
95% CI 51.4–60.0
NR NR
10.9** 8.1**
6.9–16.6 4.7–13.6
NR NR NR NR
14.9 8.4
12.1–18.3 6.2–11.2
NR NR NR NR
n = 1467. * Includes complete/partial coverage, i.e., received at least 1 dose; response was the most important reason, single response only accepted. ** Caution due to high sampling variability. *** Includes ‘don’t know’ responses. NR not releasable; unreliable estimates in one or more risk groups. Table 4 Most important reason for not receiving influenza vaccination* . Reason
%Total
95% CI
6–23 months (%)
95% CI
2–11 years with chronic conditions (%)
95% CI
2–11 years without chronic conditions (%)
95% CI
Need: not needed in general Need: child does not need Need: doctor did not recommend Need: other Concern: vaccine safety Concern: will cause influenza Concern: does not work Access: inconvenient/hard to find Fear of needles Other***
32.2 20.9 5.3 1.8** 9.6 1.3** 4.1 7.7 2.0** 15.0
29.9–34.7 18.9–23.0 4.3–6.6 1.3–2.5 8.2–11.1 0.9–2.0 3.2–5.4 6.5–9.1 1.4–2.7 13.4–16.8
28.4 29.8 9.9 NR 4.5** NR NR 5.5** NR 15.1
24.4–32.9 25.7–34.3 7.5–13.0
28.8 13.3 3.6** NR 17.3 NR NR 8.9** NR 17.6
24.1–34.0 10.0–17.4 2.0–6.2
33.9 20.1 4.5 NR 9.3 NR NR 8.1 NR 14.5
31.1–36.8 17.8–22.6 3.4–5.9
3.0–6.7
3.8–8.0 12.1–18.7
13.6–21.8
6.3–12.5 13.7–22.3
7.8–11.1
6.6–9.8 12.6–16.6
n = 3387. * Includes complete/partial coverage, i.e., received at least 1 dose; response was the most important reason, single response only accepted. ** Caution due to high sampling variability. *** Includes ‘don’t know’ responses. NR not releasable; unreliable estimates in one or more risk groups.
reported reason for influenza vaccination was a recommendation (13.1%), most often by a health professional. The most important reason for receiving influenza vaccination differed by risk group. A recommendation from a health professional was reported more often in the youngest age group at 19.7% for children aged 6–23 months (Table 3). For those who chose not to vaccinate their children in the 2006–2007 influenza season, one-third (32.2%) made a general overall comment that influenza vaccination was not needed, while a further 20.9% specifically identified that their child did not need to be vaccinated (Table 4). Almost 10% (9.6%) expressed concern about vaccine safety and a further 7.7% reported barriers to access. Five percent (5.3%) reported that vaccination was not recommended. A small percentage (4.1%) expressed concerns regarding vaccine effectiveness. Differences by risk group were also observed. Respondents with children aged 6–23 months more frequently reported that their child did not need vaccination (29.8%) or vaccination was not recommended by their doctor (9.9%). 4. Discussion This is the first population estimate of influenza vaccination coverage rates in Ontario children since the introduction of universal vaccination in 2000. Vaccination rates among high-risk children during the 2006–2007 influenza season were well below the national target of 70% [16], and for 6–23 month olds, below rates in most other Canadian provinces that target this age group.
This study was conducted in the seventh season of universal coverage in Ontario. Low vaccination coverage due to poor public awareness would seem unlikely and the majority of respondents who chose to vaccinate their children cited reasons that enhanced health, including those who specifically identified illness prevention (most frequently reported reason) or prevention of transmission. However, increasing public knowledge about the serious health risks associated with influenza and the benefits of vaccines is clearly needed [17–22]. For respondents who chose not to vaccinate their children, the most common reason related to beliefs about the lack of need for vaccination, particularly for children aged 6–23 months. In addition to ongoing public education efforts, a recommendation from a health professional is a key component to improving vaccination coverage [20–23]. This was the third most frequently reported reason among all respondents who chose to vaccinate their children and ranked second among respondents with children aged 6–23 months. For those who chose not to vaccinate their children, particularly for respondents with children aged 6–23 months, over half questioned the need for vaccination. Clear and consistent messaging regarding the risks and benefits of immunizations, including vaccine safety, is important for increasing coverage rates, and health professionals play an essential role in changing public perception [17–23]. Influenza vaccines for children are safe, but the evidence of vaccine efficacy for those aged 6–23 months is more limited [24]. Some health care professionals may have reservations about recommending routine vaccination against influenza in these
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young children, despite good evidence of the substantial burden of illness in this age group [17]. In the context of a universal vaccination program, access issues were higher than expected. This reason, which included responses such as ‘inconvenient’ and ‘too busy’, may reflect less frequent physician visits in older children. This underscores the need to capitalize on all opportunities to promote influenza vaccination and to continue to provide a variety of delivery venues. The low rate in Ontario children aged 6–23 months compared to other jurisdictions with targeted programs was unexpected. Although the type of coverage data available varies by province, and comparisons are challenging due to a lack of standardization in data collection methodology and reporting definitions, we do not believe this would account for all of the observed variation. Parental knowledge, attitudes and beliefs play a key role in determining whether their children are vaccinated [20–23]. However, physician or other health professional recommendations are also important [18,20–22]. Across Canadian provinces, there is great variation in the proportion of routine childhood immunizations given by physicians versus public health nurses. Ontario and Manitoba have the highest proportion of immunizations given by physicians (personal communication, Anna-Maria Frescura, Public Health Agency of Canada). It may be that there has been lower uptake of the recommendations in this age group by physicians, possibly because the evidence suggesting that vaccine efficacy is lower in children under 2 years [24]. This study provides only a point estimate of coverage. Whether greater increases in children can be achieved under a universal program compared to targeted programs, as previously reported in Ontarians aged 12 years and older with and without chronic conditions [9,10], requires regular reporting to monitor trends. Surveys are a feasible and cost-effective method for repeatedly reporting on immunization status in the absence of a comprehensive registry [25], however parental-reported data has been shown to result in over-reporting of immunization status [23]. When collecting information on immunization status, prior immunization history or the prevalence of chronic conditions, there may have been a tendency for parents to respond in a manner that would have been viewed favorably. In addition, recall bias may have been important in the recollection of whether the child was immunized and the location where the vaccination was given as the survey was conducted over a 6-month period mostly after the end of influenza season. This may have resulted in parental confusion, particularly in older children who are more likely to receive influenza vaccination from different providers and at a variety of locations As with other survey research, this study has a number of other limitations. Almost three-quarters of respondents were university or college educated; much higher than expected in the general population. The coverage rate in this study likely over-estimates actual coverage as lower education attainment has been shown to negatively predict influenza and other vaccination in children [20,26]. Selection bias, which is not unique to survey research, cannot be ruled out as some households refused to participate while other eligible households may have chosen not to participate in the survey by reporting that they had no eligible children. Households without phone numbers, estimated at less than 2% [27], and households with only mobile telephones, estimated at 4% [28], were excluded. These households may differ from the study population and their impact on the study’s provincial coverage rates is unknown. In summary, influenza vaccine coverage rates in high-risk children across Canada are below national targets and funding universal access alone is unlikely to achieve these goals. Although the universal program in Ontario has achieved moderate rates of immunization overall, and higher rates in many high-risk populations compared to provinces with targeted programs, this is not the case for children aged 6–23 months. However, improving cov-
erage will require routinely available immunization data. Ontario is not amongst the Canadian provinces that have implemented population-based immunization registries. This lack of a registry has hindered efforts to provide ongoing monitoring of vaccine uptake, provide timely access to information to inform influenza vaccination planning and evaluation, and provide opportunities for health professionals to implement public health strategies to specifically target groups with low coverage [29], including children aged 6–23 months. Ensuring the success of a universal vaccination program must include the ability to assess coverage in all populations, especially those designated as high-risk. Acknowledgements We thank Charles Burchill and Wendy Au, Manitoba Centre for Health Policy, Rosalie Tuscherer, Saskatchewan Health, and Elaine Sartisan, Alberta Health and Wellness, for providing estimates of influenza vaccination coverage for children aged 6–23 months from their respective provinces. Contributions: Ms Moran had full access to all the Ontario survey data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Moran, Maaten, Guttmann, Northrup and Kwong. Acquisition of data: Northrup and Kwong. Analysis and interpretation of data: Moran, Maaten, Guttmann, Northrup and Kwong, Drafting of the manuscript: Moran and Kwong. Critical revision of the manuscript for important intellectual content: Moran, Maaten, Guttmann, Northrup and Kwong. Statistical analysis: Moran. Obtained funding: Moran, Guttmann and Kwong. Administrative, technical and material support: Moran, Maaten and Northrup. Study supervision: Moran and Kwong. Financial disclosure: Ms Moran and Maaten, Drs Kwong and Guttmann, and Mr. Northrup certify that all affiliations with or financial involvement, within the past 5 years and foreseeable future with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript of completed disclosed. Funding/support: This study was supported by the Canadian Institutes of Health Research (CIHR), Institute of Infection and Immunity, and Public Health Agency of Canada, Centre for Infectious Disease Prevention and Control, Research grant no. XIN 82408. Dr. Guttmann is supported in part by a CIHR New Investigator Award. Dr. Kwong was supported by a CIHR Fellowship Award at the time of the study and is currently supported by an Ontario MOHLTC Career Scientist Award and a University of Toronto, Department of Family and Community Medicine Research Scholar Award, and also receives some salary support from the ICES. This work was made possible with the support of ICES, which is funded in part by the Ontario MOHLTC. The opinions, results and conclusions are those of the authors, and no endorsement by the Ontario MOHLTC, ICES, or Manitoba Health and Healthy Living is intended or should be inferred. Role of the sponsor: Design and conduct: None. Collection, management, analysis and interpretation of the data: None. Preparation, review or approval of the manuscript: None. Additional contributions: None to report. References [1] Canada NewsWire. Ontario invests $38 million to ease emergency room pressures with universal vaccination program. http://ogov.newswire.ca/ontario/ GPOE/2000/07/25/c6018.html?lmatch=&lang=.html, 2000 July 25 [cited 2007 July 9];. [2] Public Health Agency of Canada. Canadian Immunization Guide. 7th ed. Ottawa: Her Majesty the Queen in Right of Canada; 2006. [3] National Advisory Committee on Immunization (NACI). Statement on influenza vaccination for the 2003–2004 season. Canada Communicable Disease Report 2003;29:1–20.
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