Childhood immunization in the 1990s

ELSEVIER

Childhood Immunization in the 1990s Ruth Ann Dunn, MD

Pediatrics Update

DEPARTMENT OF PEDIATRICS/HUMAN DEVELOPMENT, MICHIGAN STATE UNIVERSITY, EAST LANSING, MICHIGAN, U.S.A.

Ahstract

Introduction

The science and practice of immunization has become among the fastest growing and changing fields in medicine. Despite growing knowledge and access to new and better vaccines, young children are not being immunized on time, largely due to missed opportunities to immunize them while they are in the doctor's office. Concerted efforts are now underway to improve childhood immunization levels nationwide. Standards have been published to guide practitioners in the provision of appropriate immunization services. The routine childhood immunization schedule is updated and published annually. New recommendations for the 1997 routine childhood immunization schedule will include the incorporation of the inactivated poliovirus vaccine into the regular infant polio vaccination series; and the licensure of and recommendation for use of acellular pertussis vaccines for infants. Recent additions to the childhood vaccine armamentarium are hepatitis A and varicella vaccines. This review will cover these and other topics and point the practitioner to resources for maintaining current knowledge in the field of childhood immunization. © 1996 Elsevier Science Inc. MEDICAL UPDATE FOR PSYCHIATRISTS 1;5:149-153, 1996.

Over the past 10 years, the science and practice of immunization has become among the fastest growing and changing fields in medicine. Before 1986, changes occurred primarily in the formulation of existing products, such as diphtheriatetanus-pertussis (DTP) vaccines, or in the combining of existing vaccines, such as measles-mumps-rubella (MMR). Since 1986, there has been an explosion in vaccine research and development. No fewer than 35 new vaccines are under development, many of them for diseases for which a vaccine does not yet exist. In the last 10 years, five new vaccines were added to the routine childhood immunization schedule: Haemophilus influenzae type b (Hib), diphtheriatetanus-acellular pertussis (DTaP), DTP-Hib combination, hepatitis B, and varicella. At least two more--rotavirus and hepatitis A--will likely become part of the childhood schedule of vaccinations before the end of the decade. Recommendations continue to evolve as we gain more experience with the vaccines and the diseases for which they were developed. This means that practitioners caring for ehitdren need to have current information on the immunization schedule, available vaccines, and immunization practices. This review will cover these topics and point the practitioner to resources for maintaining current knowledge in the field of childhood immunization.

Epidemiologu The goal of immunization is to prevent disease. In the United States, most vaccine-preventable diseases are at an alltime low; six diseases are targeted for

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elimination by 1996 (Table 1). Disease elimination strategies involve achieving and maintaining high levels of immunity in the population and effecting aggressive control measures when a case of a vaccine-preventable disease occurs. Some diseases are not yet targeted for elimination, either because the vaccine has not been in use long enough (e.g., hepatitis B vaccine) or because challenges still need to be overcome before the disease can be eliminated through vaccination. An example of the latter is pertussis. In 1993, the United States experienced the largest resurgence of pertussis in over 20 years. Infants and young children were most affected for two reasons: 1) Adults infected with pertussis are the primary source of the disease in young children ( 1 ). Controlling this disease will continue to be difficult until a vaccine that is safe and effective for adolescents and adults is licensed and recommended for use; 2) most of the affected children were not immunized with at least the primary series of a DTP-containing vaccine (2). This latter point underscores the main problem with controlling vaccine-preventable diseases: Most cases of vaccine-preventable diseases occur because the vaccine was not given. The measles outbreak during 19891991 drew attention to the problem of underimmunization of 2-year-olds in the United States. School immunization laws have been very effective in ensuring that school-aged children are fully immunized, but there is no such "gatekeeper" for infants and toddlers. As a result, the Centers for Disease Control and Prevention (CDC) launched a program, now known as the Childhood Immunization Initiative, to address this problem, which includes ongoing monitoring of childhood immunization levels. Presently, a median of 77% of U.S. 2-year-olds are immunized with 4 DTP, 3 polio, and 1 MMB vaccine. Immunization levels by state vary from 64% to 88% (3). The national goal is to have ->90% of 2-year-olds immunized for age before the end of 1996.

R. A. Dunn

M E D I C A L UPDATE FOR PSYCHIATRISTS

Table 1. Cases of Vaccine-Preventable Diseases--United States, 1995" Disease

No. of Cases

No. of Cases in Children Aged <5 yr

Congenital rubella syndrome Diphtheriab

7 0 1176 10,176 294 850 4509 0 149 37

6 0 271 81 107 153 2445 0 19 2

H aemoph ilus influenzae t' Hepatitis B Measles ~ Mumps Pertussis Poliomyelitis, paralytic h Rubella b Tetanus b

Source: CDC. Monthly immunization table. M M W R 1996;45:99. Data are provisional. b Diseases targeted for elimination in 1996.

Why are immunization levels low? Studies of public clinics and private physician office practices showed that health care providers were missing opportunities to immunize children while they had them in their offices ( 4 - 6 ) . Examples of missed opportunities include not assessing the child's immunization status at every visit, not giving all needed vaccines at the same visit, and not immunizing children with minor illnesses (not a true contraindication). Some practitioners believe that parents not bringing their children to the office is a primary cause of undervaccination. In fact, on average, 2-year-aids have been to a health care provider 10 times, which is twice the number of visits required to be fully immunized by age 2 ( C D C and Michigan Department of Community Health, unpublished data). The health care system also creates barriers to timely immunization. Practices that require an appointment for a well child visit or a physical examination before immunizations are given make it harder for parents to get their children immunized. Cost of vaccines is also a barrier. The cost of vaccines to fully immunize a child by age 2 may be as much as $350. Current efforts are underway, such as the federal Vaccines for Children program, to make vaccines available free or at low cost in the doctor's office so that families do not have to be referred elsewhere for vaccination services.

The Childhood immunization Schedule Table 2 shows the 1996 schedule of routine childhood immunizations in the

United States. This schedule undergoes frequent changes. A revised schedule will be published each January in a number of periodicals by CDC, the American Academy of Pediatrics (AAP), and the American Academy of Family Physicians. Each vaccine has a recommended age for administration; however, there is a range of acceptable ages for most vaccines. In principle, it is always best to give immunizations as soon as they are due to provide optimal protection to the child. More than one vaccine is available for immunizing against some diseases. The footnotes to the schedule of routine childhood immunizations should be reviewed for further information about product choices. Schedules have been developed for children who start their immunization series late or who are behind in their immunizations. These are published in the AAP Red Book and in the Morbidity and Mortality Weekly Report as an Advisory Committee on Immunization Practices (ACIP) Recommendation statement (7,8). These schedules should be used in these circumstances because they ensure that the child will receive optimal protection as quickly and safely as possible.

provider groups including the AAP, recommends 18 practices that practitioners should follow to provide timely, safe vaccination and eliminate missed opportunities ( Table 3 ) (9). Two principles deserve special mention: 1. All immunizations that are due should be given at the same visit. At some visits, three and four injections may be required. This recommendation has caused some concern among parents and providers. While there is no evidence that receiving multiple immunizations interferes with the immune response, potentiates side effects such as fever, or causes the child significantly increased discomfort, providers may still be unwilling to give more than two or three injections per visit (6). Further, studies demonstrate that physician attitudes are associated with parents" decisions to accept or refuse multiple injections per visit(10,11). This issue will challenge providers and parents for some time to come as new vaccines are licensed for use in young children. However, new combinations of vaccines will eventually become available to reduce tile number of injections required. 2. Parents need to be given time to read the Important Information Statements that describe each vaccine and have an opportunity to ask questions of the provider before giving consent for immunization. These statements have been greatly simplified over the past 2 years and are written at a more appropriate grade level for most parents. As described in the next section, parents and practitioners will have more vaccines to choose from, and parents should make an informed choice with the help of their child's health care provider.

Recent Changes, and Changes on the Horizon Important Immunizing Principles for the 1990s Immunizing is more than just following the schedule. The practice of immunization begins before the child arrives at the office and ends well after he or she leaves. The Standards for Pediatric Immunization Practices, developed by the National Vaccine Adviso~ Committee of the Department of Health and Human Services and endorsed by many

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There are many exciting developments in childhood vaccination. Two new vaccines have been licensed for young children-varicella and hepatitis A (HAV) vaccines-although only varicella vaccine is routinely recommended at this time. Varicella vaccine is appropriate for children 12 months and older who have not already had wild-type (natural) varicella infection. It is especially appropriate for susceptible adolescents mad adults, in whom

MEDICAL UPDATEFOR PSYCHIATRISTS

Childhood hnmunization in the 1990s

Table 2. Recommended Childhood Immunization Schedule United States, July-December 1996

Vaccines are listed under the routinely recommended ages. Bars indicate range of acceptable ages for vaccination. Shaded bars indicate catchup vaccination: at 11-12 years of age, hepatitis B vaccine should be administered to children not previously vaccinated, and Varicella Zoster Virus vaccine should be administered to children not previously vaccinated who lack a reliable history of ehiekenpox Age Vaccine

Hepatitis B a'b

Birth

1 month

2 months

4 months

Hep B-1

I

[

Hep B-2

6 months

12 months

15 months

18 months

4-6 years

II-12 years

14-16 years

[[ Hep B-3

Diphtheria, Tetanus, Pertussis C

DTP

H. i~uenzae type b d

Hib

Hib

Polio"

OPVe

OPV

DTP

DTP ~(DTaP at 15 + m)

DTP

I DTPoF ITd DTaP

Hib ~/

Hiba

I OPV

[ OPV

Measles, Mumps, Rubella f

I

MMR

Varicella Zoster Virus Vaccine z

I

MMR f [ ~ MMR f

Var

Approved by the Advismy Committee on hnmunization Practices (ACIP), the American Academy of Pediatrics (AAP), and the American Academy of Family Physicians (AAFP). ° Infimts bot~ to HBsAg-negative mothers should receive 2.5 #g of Merck wmcine (Rccombivax HB) or 10 #g of SmithKline Beecham (SB) vaccine (Engerix-B). The 2nd dose should be administered ->1 month after the first close. Infants born to HBsAg-positive mothers should receive 0.5 ml hepatitis B immune globulin (HBIG) within 12 h of birth, and either 5 #g of Merck vaccine (Recombivm; HB) or 10 ~zg of S B vaccine (Engerix-B) at a separate site. The second dose is recommended at 1 2 months of age and the third dose at 6 months of age. h~mts born to mothers whose HBs'Ag status is unknown should receive either 5 #g of Merck vaccine (Reeombiw~x HB) or 10 #g of SB vaccine (Engerix-B) within 12 h of birth. The second dose of vaccine is recommended at 1 month of age mad the third dose at 6 months of age. ~'Adoleseents who have not previously received 3 doses of hepatitis B vaccine should initiate or complete the series at the 11-i'2 year-old visit. The second dose should be administered at least i month after the first dose, and the third dose should be administered at least 4 months after the first dose and at least 2 months after the second dose. DTP4 may be administered at 12 months of age, if at least 6 months have elapsed since DTP3. DTaP (diphtheria and tetanus toxoids and acellular pertussis vaccine) is licensed for the fourth and/or fifth vaccine dose(s) for children aged > 1 5 mos and may be preferred for these doses in this age group. Td (tetanus and diphtheria toxoids, adsorbed, for adult use) is recommended at 11-12 years of age if at least 5 years have elapsed since the last dose of DTP, DTaP, or DT. Three H. it~uenzae ~ape b (Hib) conjugate vaccines are licensed for infant use. If PRP-OMP (PedvaxHIB [Merck]) is administered at 2 aud 4 months of age, a dose at 6 months is not required. Alter completing the primary, series, any Hib conjugate wmcine may be used as a booster. Oral poliovirus vaccine (OPV) is reeommended for routine infant vaccination. Inactivated polim~ms vaccine (IPV) is recommended for persons with a congenital or acquired immune deficiency disease or an altered immune status as a result of disease or immnnosuppressive therapy, as well as their household contacts, and is an acceptable 'alternative for other persons. The primary 3-dose series tbr IPV should be given with a minimnm interval of 4 wks between the first and second doses and 6 months between the second and third closes. fThe second dose of"MMR is routinely recommended at 4 - 6 years of age or at 11-12 years of age, hut may be administered at any visit, provided at least 1 month has elapsed since receipt of the first dose. ; Varieella zoster virus vaeeine (Var) can be administered to susceptible children any time after 12 months of age. Unvaccinated children who lack a reliable history of chiekenpox should be vaccinated at the 11-12 year-old visit.

the risk of complications with varieella infection is greater than in children. Evidence suggests that immunity conferred by the vaccine is long lasting. The efficacy of the vaccine ranges between 70% and 90%, depending upon the population. However, cases of "'breakthrough varicelia'" in vaecinees are much milder. As with any newly licensed vaccine, there is still a lot to be learned; however, the I weight of evidence about health benefits and cost effectiveness thus far should prompt providers to offer this vaccine routinely to patients for whom it is indicated (12,13). Hepatitis A virus infection is an important health problem in many parts of

the world and among special populations in the United States, such as certain Native-American groups. Children infected with HAV tend to be asymptomatic and their illness may go undetected, which can facilitate transmission to adults and other children. HAV vaccine is presently indicated only in certain settings and situations, such as travel to a country where HAV is endemic. Manufacturers are developing combination vaccines that will protect ctfildren against both HAV and hepatitis B virus (HBV). Once these products are available, hepatitis A vaccine will likely become a routinely recommended vaccine for children. Another hepatitis vaccine has been 151

around for several years but some practitioners still consider it new. HBV vaccine has been routinely recommended for infants since 1991. As with varieella vaccine, providers have been skeptical of the need for this vaccine in infants. However, universal infant vaccination, along with catch-up vaccination of adolescents, has been recommended as the most effective strategy for reducing the incidence of HBV infection in file United States (14,15). Two additions to the immunization schedule will be forthcoming by early 1997. One is the addition of DTaP for use in int~ants, the other is the use of enhanced inactivated poliovirus vaccine

R. A. D u n n

MEDICAL UPDATE FOR PSYCHIATRISTS

Tabla 3. Standards for Pediatric Immunization Practices. 1. Immunization services are readily available. 2. There are no barriers or unnecessary prerequisites to the receipt of vaccines. 3. Immunization services are available free or for a minimal fee. 4. Providers utilize all clinical encounters to screen and, when indicated, imnmnize children. 5. Providers educate parents and guardians about immunization in general terms. 6. Providers question parents or guardians about contraindications and, before immunizing a child, inform them in specific terms about the risks and benefits of the immunizations their child is to receive. 7. Providers follow only true contraindications. 8. Providers administer simultaneously all vaccine doses for which a child is eligible at the time of each visit. 9. Providers use accurate and complete recording procedures. 10. Providers coschedule immunization appointments in conjunction with appointments for other child health services. 11. Providers report adverse events following immunization promptly, accurately, and completely. 12. Providers operate a tracking system. 13. Providers adhere to appropriate procedures for vaccine management. 14. Providers conduct semiannual audits to assess immunization coverage levels and to review immunization records in the patient populations they serve. 15. Providers maintain up-to-date, easily retrievable medical protocols at all locations where vaccines are administered. 16. Providers operate with patient-oriented and community-based approaches. 17. Vaccines are administered by properly trained individuals. 18. Providers receive ongoing education and training on current immunization recommendations.

(eIPV) for the first two doses of the polio vaccination series. Whole-cell pertussis vaccine is known to cause mild side effects such as redness, soreness, swelling, and a low-grade fever in a third to a half of recipients. DTaP causes fewer side effects because it is made from one or more purified components of Bordetella pertussis rather than from the whole cell. Until recently, D T a P vaccines were only licensed for use in children 15 months through 6 years of age who had received their primary series of D T P vaccines. However, multiple clinical trials studying the effects of the vaccine in infants have demonstrated that DTaP is at least as effective as D T P vaccine and causes fewer side effects. Tripedia, a DTaP vaccine p r e p a r e d and distributed by Connaught Laboratories, Inc., was recently licensed for use in the primary infant series. Licensure of other manufacturers' D T a P vaccines is anticipated. The changing risk of polio in the United States has p r o m p t e d a reevaluation of our polio vaccination strategy. In 1994, the Western H e m i s p h e r e was certified to be free of wild-type poliovirus. However, in the United States,

between 8 and 10 cases of polio occur each year due to receipt of or contact with OPV. In an effort to reduce the risk of vaccine-associated paralytic polio while maintaining some reliance upon OPV for intestinal immunity against wild-type poliovirus, the ACIP recently r e c o m m e n d e d that a sequential schedule of two doses of elPV followed by two doses of OPV be the routine polio vaccination schedule for infants and children beginning in 1997 (16,17). The addition of D T a P and elPV to the routine schedule of infant immunizations will increase the number of injections per visit, because there is not yet a D T a P - H i b combination vaccine (as there is for D T P ) and elPV supplants the first two doses of orally administered poliovirus vaccine. C D C plans to conduct studies to determine what effect this may have on childhood immunization levels. Other exciting developments involve the creation and testing of new vaccines for childhood diseases that continue to cause significant morbidity. One example is a vaccine against rotavirus infection, which is the leading cause of acute diarrhea among children (18). Rotavirus vaccines will be administered orally, which will en-

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hance their acceptability and ease of introduction into the routine childhood immunization schedule.

LiabUitu: A Lingering Concern Mthough a concern prior to 1988, practitioners should not cite liability as a reason not to immunize the children in their practice. Since 1988 practitioners have been protected under the National Vaccine Injury Compensation Program, which is essentially a no-fault insurance plan for providers who immunize (19). Recipients of DTP, DTaP, DT, Td, OPV, eIPV, and MMR-containing vaccines must file claims of injury through this program and may not sue the practitioner or manufacturer directly. Compensation awards to successful claimants come from taxes collected on each dose of these vaccines. Hib and HBV vaccines will soon be added to the program as will every new pediatric vaccine as soon as it is recommended for use by the ACIP. It is more likely for a practitioner to be sued for not immunizing a child, who then contracts a vaccinepreventable illness such as Hib meningitis or chronic HBV infection, than for providing protection against these diseases through immunization.

Adolescent Vaccination: A N o w Target Group Adolescence represents a new period of risk for certain diseases, either because of Table 4. Recommended Resources on Current Vaccines and Immunization Practices. • AAP. Report of the Committee on Infectious Diseases, 1994 (1994 Red

Book) • Recommendations of the Advisory Comlnittee on Immunization Practices (ACIP), which are published as supplements to the Morbidity and

Mortality Weekly Report (MMWR). • Satellite telecourses offered regularly by the Centers for Disease Control and Prevention. Continuing Medical Education credits are awarded for completing the course. For more information, call 1-800-CDC-SHOT. • Local or state health departments. Offer resources, continuing medical education opportunities, consultation, technical assistance. • Medical schools, Departments of Pediatrics. Offer continuing medical education opportunities, consultation.

MEDICAL UPDATE FOR PSYCHIATRISTS

inadequate or waning immunity or because of the adoption of new risk behaviors. The ACIP and others have developed guidelines for addressing the immunization needs of the adolescent (20). Table 2 shows the recommended vaccinations that adolescents should receive during the l l - 1 2 - y e a r - o l d visit.

Conclusions Immunization is among the most effective and gratifying ways we can protect our patients from disease. The understanding of vaccine science and practices is evolving along with rapid development of new vaccines. The pediatrie and adolescent practitioner needs to stay current with these developments, to provide optimal protection for Iris patients. Table 4 lists some resources for continuing education in childhood immunizations and immunization practice.

References 1. CDC. Transmission of pertussis from adult to int:ant- Michigan, 1993. MMWR 1995; 44:74-6. 2. CDC. Resurgence ofpertussis--United States, 1993. MMWR 1993;42:952-3, 959-60. 3. CDC. National, state, and urban areavaccination coverage levels among children aged 19-35 m o n t h s - - U n i t e d States, July 1994-June 1995. MMWR i996;45:503-13.

Childhood hmnunization in the 1990s

4. Dietz VJ, Stevenson J, Zell ER, et al. Potential impact on vaccination coverage levels by administering vaccines simultaneously and reducing dropout rates. Arch Pediatr Adolesc Med 1994; 148:943-9. 5. CDC. Impact of missed opportunities to vaccinate preschool-aged children on vaccination coverage levels--selected U.S. sites, 1991-1992. MMWR 1994; 43:709-18. 6. Szilagyi PG, Rodewald LE. Missed opportunities for immunizations: A review of the evidenee. J Public Manage. Pract. 1996; 2:18-25. 7. Peter G, ed. 1994 Red Book: Report of the Committee on Infectious Diseases. 23rd edition. Elk Grove Village, IL: American Academy of Pediatrics, 1994. 8. CDC. General recommendations on imnmnization. Recommendations of the Advisory Committee on hnnmnization Practices (ACIP). MMWR 1994;43:138. 9. Ad Hoe Working Group for the Development of Standards for Pediatric Immunization Practices. Standards for Pediatric Immunization Practices. JAMA 1993; 269:1817- 22. 10. Freed GL, Bordley WC, Clark Sj, et al. Reactions of pediatricians to a new Centers for Disease Control recommendation for universal immunization of infants with hepatitis B vaccine. Pediatrics' 1993;91:699-70"2. 11. Woodlin KA, Rodewald LE, Humiston SG, et al. Physician and parent opinions: Are children becoming pincushions from immunizations? Arch Pediatr Adolesc Med 1995; 149:845-9.

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12. Committee on Infectious Diseases. Recommendations for the use of live attenuated varicella vaccine. Pediatrics 1995; 95:791-6. 13. CDC. Prevention of varicella: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 1996;45:1-36. 14. CDC. Hepatitis B virus: A comprehensive strategy for eliminating transmission in the United States through universal childhood vaccination. Recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 1991;40:1-19. 15. CDC. Update: Recommendations to prevent hepatitis B virus transmission-United States. MMWR 1995;44:574-5. 16. Jndelsohn R. Changing the U.S. polio immunization schedule would be bad public health policy. Pediatrics 1996; 98:115-6. 17. Katz SL. Poliovaccine policy--time for a change. Pediatrics 1996;98:116-7. 18. Cohen MB. Etiology and mechanisms of acute infections diarrhea in infants in the United States. J Pediatr 1991; 118:$34-9. 19. Evans G. Vaccine liability and safety: A progress report. Pediatr Infect Dis' J 1996; 15:477-8. 20. CDC. Adolescent immunization. Recommendations of the AdvismT Committee on hnmunization Practices (ACIP), the American Academy of Pediatrics (AAP), the American Academy of Family Physicians (AAFP), and the American Medical Association (AMA). In press.