Evaluation of a targeted hepatitis A immunization program
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Description
The purpose of this study was to evaluate the effectiveness of a hepatitis A vaccine requirement targeted at childcare center attendees aged 2--5 in Maricopa County, Arizona. Assessment of vaccine coverage shows that 13.4% of all children aged 2--5 years and 51.9% of children attending childcare have received at least one dose of hepatitis A vaccine. In addition, almost 85% of physicians surveyed agreed with the requirement. Incidence rates, for the overall population and the targeted age group, decreased following implementation A case-control study conducted prior to implementation found individuals with hepatitis A were 6 times more likely to have worked in or attended a childcare center compared to their matched controls. In addition, 40% of hepatitis A cases in the population were attributable to attending or working in a childcare center A case-control study was conducted post-implementation. Cases were individuals reported to surveillance staff between 8/1/99 and 4/30/00. Cases were included if they met the Centers for Disease Control hepatitis A surveillance case definition. Each case (n = 72) was matched to two controls (n = 144) based on age and neighborhood Cases were more likely to have had contact with a hepatitis A case (OR = 9.55, CI: 2.09, 43.67) compared to their matched controls in the unadjusted analysis. In addition, individuals with direct contact with a childcare center (OR = 0.223, CI: 0.049, 1.021) or greater than 12 years of education (OR = 0.149, CI: 0.055, 0.40) were protected against disease In the multivariate analysis, contact with a hepatitis A case (OR = 23.28, CI: 2.09, 28.35) was still significantly associated with disease. In addition, protective effects of education (OR = 0.146, CI: 0.045--0.476) and direct childcare center contact (OR = 0.065, CI: 0.004, 0.935) both remained significant. Over 12% (PAR = 12.5, CI: 3.12, 21.88) of the hepatitis A cases in the population were attributable to contact with a case The results of this study suggest the vaccination requirement has had some impact on the epidemiology of hepatitis A in Maricopa County. The risk associated with childcare centers seen in the 1997 study has either become protective or no longer significantly associated with hepatitis A disease