OBJECTIVES: Describing rates of seroconversion and its associated factors in a series of Brazilian infants following the final dose of the vaccine at 6 months of age. METHODS: Peripheral blood samples were collected after the third dose of the vaccine for the detection of anti-hepatitis B surface antibodies among infants of 7-12 months of age. We measured the association between seroconversion and birthweight, gestational age, time since administration of the vaccine in the maternity hospital and whether or not testing for hepatitis B surface antigen had been performed during pregnancy. RESULTS: We examined 40 infants. The mean birthweight was 2787 g (standard deviation = 853 g) and mean gestational age was 37.5 (standard deviation = 3.08) weeks. The proportion that seroconverted was non-significantly higher in infants who weighed >2000 g at birth (96.7%) than in those with birthweights <2000 g (80%, p = 0.149). There was no difference between the infants who were born at <37 weeks of gestational age and those born at >37 weeks (p < 0.178) neither between seroconversion and the time of application of the first dose of the vaccine after delivery (p = 0.202). CONCLUSION: The proportion of infants who seroconverted was similar to that found in other Brazilian studies. There were no differences in the proportion seroconverting by age at first immunization.
Newborn infant; Prematurity; Hepatitis B vaccine; Seroconversion
