Non-specific effects of routine vaccinations on child survival between 12-59 months of age in Jigawa, Nigeria: A secondary analysis of the INSPIRING Jigawa trial.

Nigeria contributes a substantial number of under-5 deaths and 'zero dose' children (i.e. children with no routine vaccinations) to the global burden each year. Vaccines are a lifesaving intervention proven to reduce child mortality from specific diseases. Non-specific effects of vaccines may further affect all-cause child mortality. This analysis explores the association between vaccination status and child survival for children 12-59 months of age, using data from the INSPIRING trial in Jigawa, Nigeria (registration: ISRCTN39213655). Descriptive analysis and logistic regression were used, with multivariate models adjusting for the study design and child age, sex, malnutrition, maternal education, maternal age, compound size and wealth quintile. Interaction effects for child sex were explored given evidence for non-specific effects of vaccines. We found all groups of vaccinated children to have reduced mortality compared to unvaccinated children. Children that completed the Nigerian vaccination schedule, i.e. received the second measles vaccine dose, had the lowest odds of death, with a 70 % reduction in mortality compared to an unvaccinated child (AOR: 0.30, CI: 0.18, 0.49, p-value <0.001). A child that had basic antigens and the 1st measles dose had 30 % lower odds of death than an unvaccinated child (AOR: 0.70, CI: 0.49, 0.98, p-value 0.038). This study supports evidence that vaccines have non-specific effects on all-cause child mortality. Unvaccinated children had the highest odds of death between 12 and 59 months of age and must be reached through vaccination to improve their chances of survival. In this setting, receiving a second measles vaccine was associated with a large reduction in child mortality, and may be an effective focus for outreach campaigns in Northern Nigeria.