Journal of Bioanalysis & Biomedicine

The Potency of Yellow Fever Vaccines Sold in Open Markets in Eastern Nigeria

Abstract

Godwin Chukwuma, Linda Okoye, Kenneth Ngwoke and Charles Esimone

Background: There has been a re-emergence of Yellow Fever (YF) disease across Africa and in South America since the 1980s. According to WHO estimate, 508 million people in 32 countries are at risk because of their location in the rainforest region, the habitat of the vector mosquito.Intense YF virus circulation occurred in West Africa in 2008 and 2009 with outbreaks reported from Burkina Faso, Cameroon, Central African Republic, Chad, Congo, Côte d’Ivoire, Guinea, Liberia and Sierra Leone. Between January 2010 and March 2011, outbreaks of YF were reported to the WHO by Cameroon, Côte d’Ivoire, Democratic Republic of Congo, Sierra Leone, Senegal and Uganda. Most recent outbreaks in Africa were reported simultaneously in Ghanaand Cameroun on the 3rd of February, 2012.This study investigates a possible correlation between vaccine manufacture, cold chain handling and vaccine potency/ stability as a risk factor in the repeated outbreak of yellow fever in the face of increased immunisation coverage in Nigeria and West Africa by extension. Methods: Samples of Stamaril®, a yellow fever vaccine collected from different open market sources were subjected to potency test by measuring their immunogenicity indicators.Their embryo infectivity dose and mice LD50 as well as their pyrogenicity were determined. Results: Results showed that 42% of the vaccines tested were not suitable for use even though the vaccine vial monitor certifies they are fit for use. Conclusion: A large proportion of YF vaccines sold in open markets in Eastern Nigeria may be compromised in terms of potency. Vaccine vial monitors only are not entirely reliable as indicators of vaccine potency or usability.