Immunogenicity of hepatitis B vaccine in premature infants.

The immunogenicity of plasma-derived hepatitis B vaccine was studied in 39 premature neonates, whose weights were 1,800-2,400 g and gestational ages 32-37 weeks. All maternal antiHBc antibody were negative. Dosage of 5 micrograms of hepatitis B vaccine (Pasteur vaccine) was given at 0, 1, 2 and 12 months after birth. At the ages of 1, 2, 4, 9, 12 and 13 months, antiHBs antibody was found in 7.7%, 20%, 69.7%, 81.4%, 77.3% and 89.5%, respectively, while the geometric mean titer in this seropositive group, starting at age 2 months was 37, 121, 113, 69 and 1,016 mIU/ml. There was no severe reaction attributed to the vaccination. The result indicated that the vaccine was immunogenic. Although the conversion rate was low after primary injection, a satisfactory response developed at age 4 months after 3 doses of vaccine.