Impact of Thimerosal-Related Changes in Hepatitis B Vaccine Birth-Dose Recommendations on Childhood Vaccination Coverage

CONTEXT In July 1999, the longstanding preference to begin hepatitis B vaccination of all US infants at birth was temporarily suspended because of concerns about exposure to mercury contained in the vaccine preservative thimerosal. The suspension was lifted in September 1999 when preservative-free hepatitis B vaccine became available. OBJECTIVE To determine the effects of changes in recommendations regarding administration of a hepatitis B birth dose on vaccination coverage. DESIGN, SETTING, AND PARTICIPANTS Cohort analysis of vaccination status of 41 589 US children born before, during, and after the recommendation to suspend the birth dose. MAIN OUTCOME MEASURES Association between birth cohort and age at receipt of hepatitis B vaccine dose 1, and receipt by 19 months of age of all recommended vaccines. RESULTS The proportion of US infants who received dose 1 of hepatitis B vaccine at birth declined from 47% among those born 7 to 12 months before the suspension to 11% among those born during the suspension. Birth-dose coverage remained significantly lower in the year after the suspension was lifted (23% in the first 6 months and 33% in months 7-12). Coverage with 3 doses of hepatitis B vaccine by 19 months of age declined from 88% among those born 7 to 12 months before the suspension to 81% among those born during the suspension and 85% among those born in the 6 months after the suspension, but returned to baseline levels for those born 7 to 12 months after the suspension was lifted. These reductions represent 750 000 fewer newborns vaccinated during 2000 compared with 1998, and an excess 182 000 children undervaccinated for hepatitis B at 19 months of age compared with 1998 coverage levels. Coverage with other recommended vaccinations did not decline over this time. CONCLUSIONS Reductions in hepatitis B vaccine birth-dose coverage persisted after recommendations were made to resume previous newborn vaccination practices. Although the recommendation to complete the series by 19 months of age was never changed, infants born between July and December 1999 were less likely to have completed the series by 19 months, compared with infants born during the previous year. The lack of impact on other vaccinations suggests that public confidence in immunization remained strong.