Comparison of immunogenicity of combined DPT--inactivated injectable polio vaccine (DPT - IPV) and association of DPT and attenuated oral polio vaccine (DPT + OPV) in Pakistani children.

Two hundred children aged 2-24 months attending EPI Centre Rawalpindi General Hospital, were randomly assigned to two basic immunization schedules i.e. 3 doses of oral polio vaccine alongwith two doses of DPT (Conventional Schedule) and 2 doses of combined DPT - enhanced injectable polio vaccine (new simplified schedule). Comparison of the seroconversion results showed the presence of protective antibodies against all the 3 types of polio in 100% of the children in both the groups, but there was no statistical difference in the geometric mean antibody titre in the two immunization schedules. After two doses of DPT-IPV or DPT vaccine alone the results demonstrated antibody levels above the protective threshold in both the groups against Diphtheria, Pertussis and Tetanus.