National immunisation campaigns with oral polio vaccine may reduce all-cause mortality: An analysis of 13 years of demographic surveillance data from an urban African area.

BACKGROUND Between 2002-2014, Guinea-Bissau had 17 national campaigns with oral polio vaccine (OPV) as well as campaigns with vitamin A supplementation (VAS), measles vaccine (MV), and H1N1-influenza vaccine. We examined the impact of these campaigns on child survival. METHODS We examined the mortality rate between day 1 and 3 years of age of all children in the study area. We used Cox models with age as underlying time to calculate adjusted mortality rate ratios (MRR) between "after-campaign" mortality and "before-campaign" mortality, adjusted for temporal change in mortality and stratified for season at risk. RESULTS Mortality was lower after OPV-only campaigns than before, the MRR for after-campaign vs. before-campaign being 0.75 (95% CI=0.67-0.85). Other campaigns did not have similar effects, the MRRs being 1.22 (1.04-1.44) for OPV+VAS campaigns, 1.39 (1.20-1.61) for VAS-only campaigns, 1.32 (1.09-1.60) for MV-with-VAS campaigns, and 1.13 (0.86-1.49) for the H1N1 campaign. Thus, all other campaigns differed significantly from the effect of OPV-only campaigns. Effects did not differ for trivalent, bivalent, or monovalent strains of OPV. With each additional campaign of OPV-only, the mortality rate declined further (MRR=0.86 (0.81-0.92) per campaign). With follow-up to 3 years of age, the number needed to treat (NNT) to save one life with campaign-OPV-only was 50 neonates. CONCLUSION OPV campaigns can have a much larger effect on child survival than otherwise assumed. Stopping OPV campaigns in low-income countries as part of the endgame for polio infection may increase child mortality.