Estimation of Live Virus Content of Yellow Fever Vaccine by Tissue Culture Technique

Abstract

Summary

Efforts to develop yellow fever vaccines began soon after the isolation of the virus in 1927. Use of the French Neurotropic vaccine began in the 1930s and proved to be effective, but this vaccine was discontinued in 1982 because of the unacceptably high incidence of adverse events, especially encephalitis . All current yellow fever vaccines are derived from the 17D strain, 2 main lineages of the 17D line (17D204 and 17DD) were used for vaccine production . Since there is no specific antiviral drugs available for yellow fever, the use of live attenuated yellow fever vaccine was recommended for children of age 6-9 month and individuals traveling to regions where yellow fever is endemic. The potency of live attenuated yellow fever vaccine collected from ten (10) different hospitals/immunization centers in Maiduguri were determined using Vero cell line obtained from National Polio Laboratory Maiduguri by micro titration method. The seven (7) different batches of yellow fever vaccines (606, 604, 612, 614, 720, 726 and 9945781A) collected from primary immunization centre (NH, SH and USH) show low/lost potency which consequently may affect their efficacy as compare to WHO standard titer of 10 ten dose/ vial. This may be linked to inadequate storage facility at the primary immunization centers, poor power supply (lack of 24hrs stand by generator/power back up) and lack of strict adherence to WHO guidelines for yellow fever vaccine storage /administration are possible factors to the low titer vaccine obtained in this study. Thus, improvement of these facilities within the vaccine storage and distribution network is therefore advocated to keep the yellow fever vaccine at the optimal WHO standard titer.