Evaluation of a recombinant DNA hepatitis B vaccine in a vaccinated Nigerian population.

INTRODUCTION Recombinant hepatitis B vaccine was introduced in 1986 and has gradually replaced the plasma-derived hepatitis B vaccine. No published data are available on the immunogenicity of hepatitis B vaccines in Nigerians. The current study aimed to evaluate protective sero-conversion rates after vaccination with Shanvac-B rDNA hepatitis B vaccine in Nigerian subjects between January and September 2009. METHODOLOGY   After having obtained informed consent and ethical clearance, 2 mL of blood were aseptically collected from each participant aged ≤50 years, one month after the first, second and third doses of the vaccine. Sera were separated into cryovials and frozen at -21oC until analysed for the detection of the protective antibody titre induction. Protective antibody titre was defined as a titre of ≥10 mIU/mL. RESULTS Of the 376 participants, 192 (51.1%) were males and 184 (48.9%) were females. A total of 144 subjects participated in the first-dose group, nine (6.3%) of whom developed protective antibody titre (8.3% of males and 4.2% of females). Of the 121 participants in the second-dose group, 108 (89.3%) developed protective antibody titre (98.3% of males and 80.3% of females), while of the 111 participants in the third-dose group, 100% protectively sero-converted. Males were more likely to develop protective antibody titre than females after the second dose (P < 0.05). CONCLUSION This data provides additional evidence for the efficacy of Shanvac-B rDNA hepatitis B vaccine and the need to adhere to the recommended three-dose schedule to achieve full and lasting sero-protection among Nigerians.