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ELECTRONIC ARTICLE |
* Immunization Services Division, National Immunization Program, Centers for Disease Control and Prevention, Atlanta, Georgia
Data Management Division, National Immunization Program, Centers for Disease Control and Prevention, Atlanta, Georgia
Division of Viral Hepatitis, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia
|| Butte County Department of Public Health, Oroville, California
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ABSTRACT |
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Methods. A random cluster sample survey was conducted of parents of children who attended kindergarten in Butte County, California, in 2000. Because of a history of recurrent epidemics, an aggressive hepatitis A vaccination program was ongoing during the time this study was conducted. Receipt of 1 or 2 doses of hepatitis A vaccine was studied.
Results. Of 896 surveys sent, 648 (72%) were completed. The vaccination coverage for at least 1 dose of hepatitis A vaccine was 398 (62%) and for 2 doses was 272 (42%). Factors associated with not receiving the vaccine included lack of provider recommendation (vs having recommendation; odds ratio [OR]: 7.8; 95% confidence interval [CI]: 4.9–12.2), not having heard of the vaccine (OR: 2.4; 95% CI: 1.2–4.9), and parent’s not perceiving child is likely to get hepatitis A (vs perceiving child might get disease; OR: 2.1; CI: 1.6–2.9).
Conclusions. Vaccination coverage among kindergartners did not reach high levels (ie, >90%), despite aggressive vaccination efforts in this community. Lack of provider recommendation and lack of parental awareness of hepatitis A vaccine were the 2 most significant factors associated with failure to receive vaccine. These findings will facilitate the development of vaccination strategies for communities in which hepatitis A vaccination is recommended.
Key Words: hepatitis A; knowledge • attitudes • and practices; vaccination
Abbreviations: CDC, Centers for Disease Control and Prevention • ACIP, Advisory Committee on Immunization Practices • BCHD, Butte County Health Department • CI, confidence interval • SES, socioeconomic status
Hepatitis A is among the most frequently reported vaccine-preventable diseases in the United States; in 2001, >11 500 cases were reported (Centers for Disease Control and Prevention [CDC], unpublished data, 2002). Because of clinically unrecognized or asymptomatic infections, especially among children, the number of infections may be up to 10 times higher.1 Because children account for at least one third of cases and also are a potential source of infection for others, routine vaccination of children is likely to be an effective way to reduce hepatitis A incidence.2 In October 1999, the Advisory Committee on Immunization Practices (ACIP) updated recommendations for hepatitis A vaccination to include routine vaccination of children age 
2 years in states, counties, and communities with hepatitis A incidence rates that were at least twice the 1987–1997 national average (20 cases per 100 000 population).2 Over time, this strategy has the potential to substantially lower disease incidence and possibly eliminate indigenous transmission of hepatitis A virus.3
Butte County is located in the Sacramento Valley of northern California and had an estimated population in 2000 of 207 000. The county has had recurrent outbreaks since hepatitis A became reportable in 1966 and meets the ACIP’s criteria for routine childhood hepatitis A vaccination.4 During 1987–1997, the average annual hepatitis A incidence rate was 45.3 per 100 000 (CDC, unpublished data, 2001).
From January 1995 through December 2000, a demonstration project was implemented in Butte County to assess the impact of routine vaccination of children on disease incidence over time. Hepatitis A vaccine was made widely available free of charge to children aged 2 to 12 years in 1995 and to successive cohorts of 2-year-old children through public and private providers in the county. Initially, hepatitis A vaccine was administered primarily in school-based clinics. Starting in 1996, private and public health care providers administered the vaccine. To evaluate further the vaccination program, we surveyed parents and providers of kindergarten children to assess their knowledge, attitudes, and practices toward hepatitis A vaccination and to identify factors associated with not receiving hepatitis A vaccine. This report presents findings from the survey of parents.
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METHODS |
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= 0.05 and assuming that half the population was vaccinated, 60 classrooms were randomly selected, which included 901 enrolled students. For confidentiality reasons, we were not told the actual number of children per classroom. However, we were told the total number of kindergartners and the number of kindergarten classrooms for each school, from which we estimated the classroom size. The study was approved by the Institutional Review Board of the CDC. The teachers of the selected classrooms were given English and Spanish surveys to distribute to all students in their classrooms to take to their parents. Parents/legal guardians signed an informed consent form either agreeing or declining to participate in the study. Envelopes were provided so that respondents could return the consent form and survey confidentially through their child to the teacher. When a teacher did not receive a survey back from a child in 3 to 5 days, the teacher sent a reminder home with the child. After an additional 3 to 5 days, all forms and surveys that were returned to the teacher were mailed back to the Butte County Health Department (BCHD). Parents who did not respond were contacted by the BCHD and, if interested, were interviewed by telephone.
Survey Questionnaire and Outcome Measure
The survey questionnaire included questions related to demographics, health-seeking practices, and knowledge and attitudes about hepatitis A disease and the vaccine. To determine the vaccination status of students, we first used vaccination documentation contained in the BCHD hepatitis A immunization registry because all vaccinations that were given free-of-charge during the demonstration project were recorded from provider records in the registry. Second, because a child could have received the vaccine from a provider not participating in the demonstration project, a child was considered vaccinated when he or she was not included in the registry but the parent provided vaccination dates from a vaccination card on the survey. When vaccination was not recorded in the registry or by the parent-held vaccination card, the child was considered unvaccinated. Because the registry in our study was set up only as part of the demonstration project and contained information on only 1 vaccine, we did not explore the use of or accuracy of the registry.
Statistical Analyses
The study design was a random cluster sample (schools being clusters), with sampled clusters grouped into strata by school districts. Data were weighted to be generalizable to Butte County; however, although our study was designed to be related to the specific circumstances of Butte County’s demonstration project, we believe that many of the study’s important findings are likely to be generalizable to communities similar to Butte County. We examined the association between receipt of at least 1 dose of hepatitis A vaccine and selected child/parent characteristics using logistic regression to calculate odds ratios. After testing for collinearity, variables that were significant in the bivariate analyses were included in the logistic regression model. Analyses were conducted using SUDAAN, release 7.5.6 (Research Triangle Institute, Research Triangle Park, NC).
Response Rates
Of 901 parent surveys distributed, 896 met the study criterion; 5 children did not live in Butte County for at least 1 year before the survey and were excluded. The number of surveys completed and returned was 648, yielding a response rate of 72.3%. Of the 59 classrooms, the average estimated class size was 18.32 (range: 1–30). The average number of surveys returned per classroom was 11.0 (range: 1–20).
Because only 36, or 5.5%, of the entire study group reported receipt of vaccination by a parent vaccination card (with vaccination dates) but was not reported to be vaccinated by the registry, we did not further examine data for differences between those using parent-reported data not in the registry and the parent-reported data in the registry. Because the vaccine was offered free of charge by participating providers during the demonstration project, which was documented in the registry, parents would have had more incentive to take their children to those providers to receive the vaccine. Therefore, parents were probably more likely to have gone to a provider who was participating in the demonstration project and thus would be included in the registry.
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RESULTS |
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The majority of parents reported that they had heard of hepatitis A disease and of hepatitis A vaccine (Table 2). Approximately half believed that hepatitis A was a major problem in Butte County and that it was likely that their child would get hepatitis A in the county. However, almost all parents believed that it would be serious if their child were to get hepatitis A. Seventy-four percent of parents reported that they believed that the hepatitis A vaccine is safe, and two thirds believed that the vaccine should be required before school entry. Among parents of children who did not receive hepatitis A vaccine, the most commonly reported reasons given for why the child did not receive the vaccine were that they had never heard about it (32.5%), their doctor did not recommend it (20.1%), and they intended to have their child vaccinated but had not done so yet (21.5%).
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Parental knowledge and attitudes associated with not being vaccinated included not having heard of hepatitis A and the vaccine and believing that hepatitis A is not a major problem in Butte County, that it would not be serious if the child got the disease, that the child would not get the disease, that the vaccine is not safe, and that the vaccine should not be required before school entry (Table 2).
Before multivariate analysis, variables found to be highly collinear with other variables that were excluded from the model include whether the parent had heard of the disease, whether the parent believed that the vaccine was effective, and type of insurance. Variables that remained significant in the bivariate analysis were entered into the model (Tables 1 and 2). Factors that remained independently associated with not receiving at least 1 dose of hepatitis A vaccine were mother’s education, family income, not having heard of the vaccine, perceiving that the child is not likely to get hepatitis A disease, believing that kindergartners should not be required to get hepatitis A vaccine before school entry, and lack of a provider recommendation for the vaccination, which was the strongest predictor (Table 3).
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DISCUSSION |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONREFERENCES |
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The factor most strongly associated with failure to be vaccinated was not having received a doctor’s or health department’s recommendation for it. This finding is consistent with previous reports5 and underscores the critical role of provider recommendation in vaccine acceptance by parents and the importance of educating and mobilizing providers to offer hepatitis A vaccine in their offices.
Poverty and other measures of low SES, including lower education level, have been consistently reported to be strongly related to underimmunization.6,7 In our study, we found that children with mothers who had 12 or fewer years of education and children in households with <$50 000 annual incomes were more likely to have received hepatitis A vaccine than children of mothers with higher education level or in families with greater income, respectively. The hepatitis A vaccination program in Butte County was not specifically targeted toward children of low SES. However, it is possible that perception regarding likelihood of infection control and need for vaccination varied between parents in lower and higher income groups. We also do not know whether providers and others involved in the vaccination program perceived children of low SES to be at higher risk of infection and therefore in greater need to be vaccinated or whether providers of low-income children were more likely to participate in the program. A number of studies have reported that lower SES is a risk factor for getting hepatitis A.8–10
Although the vast majority of parents in our survey were aware of the vaccine, only half believed that hepatitis A was a major problem in Butte County or that it was likely that their child would get hepatitis A in Butte County. Whether parental attitudes are associated with underimmunization has been debated.11,12 Several studies have reported that parental knowledge and attitudes related to the importance of vaccination and susceptibility to disease do not explain the failure to receive vaccines.13–17 Among participants in our study, parental awareness of hepatitis A vaccine and belief regarding susceptibility of the child to hepatitis A were associated with receipt of at least 1 dose of hepatitis A vaccine. The importance of parental awareness is also suggested in our finding that lack of knowledge about the vaccine was the most frequently cited reason that the child did not receive it. Parental education, when implemented as part of a multicomponent intervention, has been shown to raise immunization coverage.18
Our vaccination coverage findings are consistent with those reported for all eligible age groups,4 including second-dose coverage that was approximately 24% to 27% lower than first-dose coverage. Immunogenicity studies have shown that virtually all children have protective concentrations of antibody when measured 1 month after receiving the first dose of vaccine.2 However, the second dose is recommended to ensure long-term protection, which is extremely important for hepatitis A because the disease can be more severe in adulthood.19
State vaccination requirements for child care and school entry are effective strategies to achieve high vaccination coverage rates among children.20 As of June 2002, hepatitis A school entry requirements were in effect in selected counties or statewide in 5 states. Our findings indicate that a hepatitis A vaccination requirement would be acceptable to the majority of parents in Butte County. However, even without a law in place, the voluntary program in Butte County was shown to have been successful in vaccinating a substantial proportion of children and seems to have resulted in dramatic declines in the incidence of hepatitis A in the county.4 The level of hepatitis A vaccination coverage needed to achieve herd immunity sufficient to reduce overall hepatitis A rates is unknown. Ongoing monitoring of hepatitis A incidence in Butte County and additional studies are needed to answer this question.
Cost of the vaccine was not a factor in Butte County, where the vaccine was provided free of charge to parents, but has been reported as a barrier to childhood vaccination, especially among poor and underserved children.7 Because the Vaccines for Children Program provides public-purchased hepatitis A vaccine to eligible children aged 2 to 18 years, who are covered by the ACIP recommendation,21 cost should not prevent vulnerable children from receiving the vaccine within their medical homes. The Vaccines for Children Program provides vaccines to public and private providers for use in children who are Medicaid-enrolled, uninsured, Native American, or Alaska Native and to children who are underinsured with respect to vaccination, but only when served at a federally qualified health center or rural health clinic.22
A potential limitation of the study is that the study’s finding that children of parents with higher SES were less likely to receive hepatitis A vaccine may be related to the specific circumstances of Butte County’s demonstration project and may not be generalizable to other communities. Another potential limitation is that we did not validate hepatitis A vaccinations by following up with the children’s health care providers. However, information on vaccinations received by 91% of the vaccinees came from the immunization registry, which contains provider-reported information, and vaccination data for the remaining children were based on documentation of vaccination dates on parent-held vaccination cards. Therefore, most of these records are likely to be accurate. In addition, provider knowledge, attitudes, and practices play a key role in vaccination of children.6,7,23 However, in this study, we did not account for the potential influence of provider knowledge, attitudes, and practices on receipt of hepatitis A vaccine by children in our study and, therefore, possibly on results of our study.
Routine hepatitis A vaccination of children has been successful in markedly reducing hepatitis A incidence in Butte County and other communities.4,24 Extending and sustaining adequate vaccination coverage levels among all children in areas with consistently elevated rates of hepatitis A should substantially reduce hepatitis A incidence nationwide. Vaccination promotion strategies should include increasing parent and provider awareness. Some states may choose to consider using child-care or school-entry vaccination requirements as a strategy to achieve high vaccination coverage levels. However, in Butte County, voluntary hepatitis A vaccination was also able to achieve coverage levels that resulted in disease reduction, especially when backed by strong provider endorsement.
Our findings suggest important implications for future research regarding the delivery of immunizations. First, because the vast majority of the children in our study received hepatitis A vaccination through the demonstration project, we could not examine the role of public purchase of vaccine in uptake and disease control, which would be particularly important for immunization programs in high-risk communities. Second, understanding doctor-patient dialogue and information sharing about the disease and the vaccine would support hepatitis educational efforts that could potentially improve immunization coverage. Finally, because new vaccines are increasingly being introduced into the market, it would be important to investigate the impact of 1 vaccine (eg, hepatitis A) program on parent and provider attitudes toward and acceptance of other recommended vaccines.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Address correspondence to Barbara Bardenheier, MPH, MA, Centers for Disease Control and Prevention, 1600 Clifton Rd, MS E-52, Atlanta, GA 30333. E-mail: bfb7{at}cdc.gov
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  P. G. Szilagyi, S. Schaffer, R. Barth, L. P. Shone, S. G. Humiston, S. Ambrose, and F. Averhoff Effect of Telephone Reminder/Recall on Adolescent Immunization and Preventive Visits: Results From a Randomized Clinical Trial Arch Pediatr Adolesc Med, February 1, 2006; 160(2): 157 - 163. [Abstract] [Full Text] [PDF]
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E. C. Owen, K. M. Peddecord, W. Wang, R. Vryheid, M. Picardal, M. DeGuire, K. W. Gustafson, S. Ross, S. K. Brodine, and M. H. Sawyer Hepatitis A Vaccine Uptake in San Diego County: Hispanic Children Are Better Immunized Arch Pediatr Adolesc Med, October 1, 2005; 159(10): 971 - 976. [Abstract] [Full Text] [PDF]
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