IMMUNE-RESPONSES OF PREMATURELY BORN INFANTS TO HEPATITIS-B VACCINATION - RESULTS THROUGH 3 YEARS OF AGE

Background. Hepatitis B vaccine is effective in infants, Preterm infan ts also respond but information on long term immunogenicity is limited . Purpose of study. To compare response of premature and full term inf ants to hepatitis B vaccine. Methods. Sixty-nine prematurely born Alas ka Native infants received three doses of hepatitis B vaccine beginnin g at discharge, Thirty-seven infants had paired serum samples drawn at similar to 1 and 3 years of life which were tested for antibody to he patitis 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 ti ters 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 wa s the decrease-in the percent of infants with titers greater than or e qual to 10 mIU/ml (preterm infants 75.7% early specimen and 8.1% late specimen compared with term infants 87% early specimen and 15% late sp ecimen), Both prematurity and longer interval between third vaccinatio n and blood sample were associated with a decreased antibody titer, No infant had evidence of hepatitis B viral infection by developing anti body to hepatitis B core antigen. Conclusions. Preterm and term infant s have a similar decline in antibody titers during the first 3 years, but preterm infants generally have a lower titer, The immunogenicity o f the vaccine beyond 3 years sind the need for revaccination in these populations requires further study.