Phased Introduction of Hepatitis B Vaccination in Pakistan

Objectives: The study was undertaken to assess the level of sero-protection of children up to five years of age who had received at least one dose of HB vaccination in their infancy. Methodology It is a cohort study to follow up vaccinated children from four weeks after completion of vaccination to one, three and five years of age of the children. The study was conducted in three districts of North West Frontier Province (N.W.F.P) from August 1991 to 1996. WHO/EMRO supplied single dose of vaccine for HBV in 1991. Five hundred randomly selected children fulfilling the inclusion criteria of having received at least one dose and 100 each of those children having received two or one dose of the vaccine: serology was conducted by using commercial ELISA. (Abbott). Results: Anti HBs was detected in 70% of infants who had received all the three doses, four weeks after completion of vaccination. After one year the sero-protection was raised to 90%, it fell to 80% after 3 years and 70% after 5 years. The group with two doses of the vaccine had anti HBs positive rates of 70%, 50% and 16% after one, three and five years respectively. The group having one dose had anti HBs positive rates of 50%, 30% and 6% and one, three and five years respectively. Conclusion: Sero conversion was best in children who had received full course and was significantly lower in those having received partial vaccination.