EClinicalMedicine (Dec 2023)
Effect of national immunisation campaigns with oral polio vaccine on all-cause mortality in children in rural northern Ghana: 20 years of demographic surveillance cohort dataResearch in context
Abstract
Summary: Background: Studies from Guinea-Bissau and Bangladesh have shown that campaigns with oral polio vaccine (C-OPV) may be associated with 25–31% lower child mortality. Between 1996 and 2015, Ghana had 50 national C-OPVs and numerous campaigns with vitamin A supplementation (VAS), and measles vaccine (MV). We investigated whether C-OPVs had beneficial non-specific effects (NSEs) on child survival in northern Ghana. Methods: We used data from a health and demographic surveillance system in the Navrongo Health Research Centre in rural northern Ghana to examine mortality from day 1–5 years of age. We used Cox models with age as underlying time scale to calculate hazard ratios (HR) for the time-varying covariate “after-campaign” mortality versus “before-campaign” mortality, adjusted for temporal change in mortality, other campaign interventions and stratified for season at risk. Findings: From 1996 to 2015, 75,610 children were followed for 280,156 person-years between day 1 and 5 years of age. In initial analysis, assuming a common effect across all ages, we did not find that OPV-only campaigns significantly reduced all-cause mortality, the HR being 0.96 (95% CI: 0.88–1.05). However, we subsequently found the HR differed strongly by age group, being 0.92 (0.75–1.13), 1.29 (1.10–1.51), 0.79 (0.66–0.94), 0.67 (0.53–0.86) and 1.03 (0.78–1.36) respectively for children aged 0–2, 3–5, 6–8, 9–11 and above 12 months of age (p < 0.001). Triangulation of the evidence from this and previous studies suggested that increased frequency of C-OPVs and a different historical period could explain these results. Interpretation: In Ghana, C-OPVs had limited effects on overall child survival. However, triangulating the evidence suggested that NSEs of C-OPVs depend on age of first exposure and routine vaccination programs. C-OPVs had beneficial effects for children that were not exposed before 6 months of age. These non-specific effects of OPV should be exploited to further reduce child mortality. Funding: DANIDA; Else og Mogens Wedell Wedellsborgs Fond.
