Potency status and efficacy of measles vaccine administered in Nigeria: a case study of three EPI centres in Lagos, Nigeria.

Abstract

The potency status and efficacy of measles vaccines were studied in three immunization (EPI) centres in the suburban area of Lagos, Nigeria. A total of 14 vials of measles vaccine were collected and subjected to potency testing while, 203 measles-vaccinated children were recruited for this study. Only 85 (41.87%) of the vaccines reported back for the post-vaccination follow-up screening. The seroconversion pattern showed that 51(60%) had potent antibody titres ranging from 1:40 to 1:1280, while the remaining 34 (40%) had a low antibody titres between < 1:20 and 1:20. The vaccine potency test showed that only 1 (7.14%) of the 14 vaccine vials collected at these centres had virus titre of 3.5 Log while the remaining 13 (92.86%) had virus titres lower than 3.0 Log: the recommended human dose by the World Health Organization (WHO) for measles vaccine. The administration of these sub potent and/or impotent vaccines vis-à-vis the status of immune response elicited in the vaccines may be one of the reasons for the occurrence of measles infection in vaccinated children in the recent time in Nigeria. We herein suggested the subjection of all vaccines to a thorough standard laboratory screening before use in Nigeria