Abstract

Background Infection and malnutrition remain significant causes of under-five morbidity and mortality in sub-Saharan Africa with a cyclical relationship between infection and malnutrition. Malnourished chil-dren are more prone to infection and would benefit from vaccination which is the most cost-effective tool available against infectious disease. However due to nutrition-induced immune suppression the malnourished child may not respond as well to vaccination. Methods We explored the relationship between undernutrition and immune responses measured by anti-body titres/IgG concentrations following one dose of yellow fever and measles vaccines in two cohorts of African children. Based on findings from our initial analysis we also assessed the lon-gevity of responses to yellow fever vaccine in a third cohort of African children. World Health Organization z-scores for weight for age, weight for height and height for age were used to as-sess nutritional status. Vaccine responses to measles and yellow fever were measured by standard ELISA and sero/micro neutralization respectively. Linear and logistic regression models were built to assess the relationships between the covariates and vaccine responses. In addition, we explored correlation of a known immune modulator which is also a nutritional factor – iron on vaccine response. Results There was significantly higher seroconversion following yellow fever vaccination in Mali com-pared to Ghana (91.0 vs 63.5% (p <0.001), and a trend to better seroconversion at higher height for age scores. Females attained significantly higher post vaccination antibody concentrations than males (p<0.001) following measles vaccination. Five to six years post yellow fever vaccina-tion within routine programmes one quarter of the children no longer had protective titers. Iron metabolism is down regulated in the first week of neonatal life. Conclusions Chronic malnutrition may negatively impact responses to yellow fever vaccines. Five to six years post routine vaccination over 25% of children were no longer protected (defined by anti-body concentrations) from yellow fever suggesting vulnerability to disease. There may be scope for considering differing vaccines doses for boys and girls for measles vaccine.

Abstract

Abstract