Immune responses of prematurely born infants to hepatitis B vaccination

BACKGROUND: Hepatitis B vaccine is effective in infants. Preterm infants also respond but information on long term immunogenicity is limited. PURPOSE OF STUDY: To compare response of premature and full term infants to hepatitis B vaccine. METHODS: Sixty-nine prematurely born Alaska Native infants received three doses of hepatitis B vaccine beginning at discharge. Thirty-seven infants had paired serum samples drawn at approximately 1 and 3 years of life which were tested for antibody to hepatitis B surface antigen. One hundred eight infants born at full term enrolled in a separate study were used for comparison. RESULTS: Both early and late blood sample antibody to hepatitis B surface antigen titers were lower in preterm than in term infants (23.1 mIU/ml vs. 56.8 mIU/ml, early blood sample; and 0.7 mIU/ml vs. 1.32 mIU/ml, late blood sample); however, these values were not statistically different. The drop in titer over time, however, was significant in both groups as was the decrease in the percent of infants with titers > or = 10 mIU/ml (preterm infants 75.7% early specimen and 8.1% late specimen compared with term infants 87% early specimen and 15% late specimen). Both prematurity and longer interval between third vaccination and blood sample were associated with a decreased antibody titer. No infant had evidence of hepatitis B viral infection by developing antibody to hepatitis B core antigen. CONCLUSIONS: Preterm and term infants have a similar decline in antibody titers during the first 3 years, but preterm infants generally have a lower titer. The immunogenicity of the vaccine beyond 3 years and the need for revaccination in these populations requires further study.