We critically carried out a potency study in 1992 and 1997 on measles and poliovirus vaccines administered at five different vaccination centers in the metropolitan Lagos, Nigeria. using WHO guidelines on titration of live- viral vaccines, our results revealed that only 6 (16.7%) of 36 measles vaccine (MV) vials and 11 (24.4%) of the 45 trivalent oral poliovirus vaccine (TOPV) vials titrated met the WHO recommended human dose. We observed that 14 (38.9%) of the total 45 polio vaccine vials titrated from different vaccination centers for both 1992 and 1997 were found to be expired or about 2 - 3 weeks to their expiry dates. Moreover, while noting the potency of the reference vaccine obtained from the national cold store to be adequate, it may not be improper to observe that the vaccines were also about 4 weeks to their expiry dates. It then suffice to say by our findings that, the inadequacies observed in our vaccines cold chains, poor vaccine handling, lack of laboratory back - up services and the administration of these sub - potent and/or, impotent expired vaccines, will be a big clog in the wheel of Nigeria towards meeting the WHO deadline of disease eradication Programme particularly, the vaccine preventable ones like measles and polio, by the year 2000. We suggested however, that education of health officers and/or, vaccinators on vaccine handling, subjection of imported vaccines to a thorough laboratory tests, discontinued distribution and non - administration of laboratory - certified expired vaccine to children are some but important remedies to the scourge of vaccine failure in Nigeria. Journal of the Nigerian Infection Control Association Vol. 1 No. 1 (Oct 1998): pp 27-33 Key Words: Potency, Viral Vaccine, Measles, Polio.
