In July 1999, the hepatitis B vaccination of all US infants at birth was temporarily suspended due to concerns about the vaccine preservative thimerosal.
This suspension was lifted in September 1999 when preservative-free hepatitis B vaccine became available.
In this study, physicians evaluated the effects of these changes on vaccination coverage.
The team performed a cohort analysis of the vaccination status of 41,589 children born before, during, and after the recommendation to suspend the birth dose.
|Coverage with other recommended vaccinations did not decline.|
|Journal of the American Medical Association|
They assessed the association between birth cohort and age at receipt of hepatitis B vaccine dose 1, as well as receipt by 19 months of age of all recommended vaccines.
The physicians determined that 47% of infants born before the suspension received dose 1 at birth, compared to 11% of infants born during the suspension.
They also found that birth-dose coverage remained significantly lower in the year after the suspension was lifted.
In addition, the team found that children who received 3 doses of hepatitis B vaccine by 19 months of age declined from 88% before the suspension to 81% in those born during the suspension. The rate increased to 85% in children born in the 6 months after the suspension, and then returned to baseline levels.
The team calculated that the reductions represent 750,000 fewer newborns vaccinated during 2000 compared with 1998. An additional 182,000 children were undervaccinated for hepatitis B at 19 months of age compared with 1998 coverage levels.
Dr Elizabeth Luman's team concluded, "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".