Background. As a result of controversy about mercury exposures from vaccines containing thimerosal, the American Academy of Pediatrics and the US Public Health Service recommended in July 1999 that the first dose of hepatitis B vaccine be deferred until 2 to 6 months of age, but only for infants born to hepatitis B surface antigen (HBsAg)-negative women. We investigated the effect of these recommendation changes on the management of Oregon infants born to women whose HBsAg status was “unknown.”
Methods. Infants were identified by reviewing electronic birth certificate data from 34 Oregon hospitals during (1)April through June 1999 [before recommendation changes (T1)], (2) August through October 1999 [after recommendations changes (T2)] and (3) April through June 2000 [when resumption of pre-1999 practices were recommended (T3)]. We verified maternal HBsAg screening and newborn hepatitis B vaccination by chart review.
Results. We identified 147 infants born to women who were not screened for HBsAg. During T1, 27% of infants born to mothers of unknown HBsAg status were vaccinated within 12 h of birth, and 80% were vaccinated before hospital discharge. This decreased to 2 and 4%, respectively, during T2 and continued to remain lower during T3.
Conclusion. Hepatitis B vaccine coverage for infants born to unscreened women declined significantly after the July 1999 announcement and remained significantly lower 10 to 12 months later. When changes are made in established vaccination practices, policy makers should ensure that such changes are not misinterpreted, resulting in failure to immunize appropriate groups.