Long-term immunogenicity and efficacy of a reduced dose of plasma-based hepatitis B vaccine in young adults

A cohort of seronegative preclinical medical and dental students and another cohort of seronegative national service recruits who were immunized intramuscularly with a reduced dose (10 mg) of plasmabased hepatitis B vaccine (Merck, Sharp & Dohme) at the start of the study and at 1 month and 6 months thereafter were followed up for 5 years and 6 years, respectively. Among the medical and dental students, antibody to hepatitis B surface antigen (antin-HBs) ([greater than or equal to10]mlU/ml)was detected in 81% of the vaccinees at the end of the 5-year follow-up and the geometric mean titre (GMT) had dropped from 412.6 mlU/ml one year after completion of vaccination to 174.9 mlU/ml after 5 years. Antibody to hepatitis B core antigen (anti-HBc) was detected in 0.4-1.0% of the vaccinees but none was positive for hepatitis B surface antigen (HBsAg) during the follow-up period. Among the national servicemen, the anti-HBs seroconversion rate and GMT were considerably lower than those of the preclinical medical and dental students. At the end of the 6-year follow-up, 55% of the vaccinees were positive for anti-HBs ([greater than or equal to]10 mlU/ml) and the GMT had dropped from 80.7 mlU/ml one year after completion of vaccination to 30.4 mlUml after 6 years. Anti-HBc was detected in 8 (2.7%) and transient Hbs antigenaemia in 2 (0.7%) of 293 vaccinees after 4 years. However, none of the 196 vaccinees followed up at 6 years was HbsAg-positive compared with 8 (4.2%) of 191 seronegative national service recruits who were not vaccinated, giving a vaccine efficacy of 100% in the prevention of the chronic HBsAg carrier state.
Introduction When hepatitis B vaccine first became commercially available, it was extremely expensive. Clinical trials on the immunogenicity of reduced doses of the vaccine were therefore conducted in several ocentres. [...]