National polio vaccine campaigns reduce all-cause child mortality
Oral polio vaccine campaigns have a larger impact on all-cause child mortality than previous research suggested, according to a study conducted in West Africa.
Researchers calculated a 25% reduction in the mortality rate after polio vaccination campaigns in Guinea-Bissau, and no similar effect from other campaigns.
“Live vaccines, including oral polio vaccine (OPV), have a much larger effect on child survival than usually assumed,” Peter Aaby, PhD, DMSc, an anthropologist and founder of the Bandim Health Project in Guinea-Bissau, told Healio. “There was no polio infection in Guinea-Bissau in the study period, so the beneficial effects are entirely nonspecific.”
Aaby and colleagues analyzed the impact of 17 national campaigns providing OPV, vitamin A supplementation (VAS), measles vaccine and H1N1 influenza vaccine from 2002 to 2014 in Guinea-Bissau. They evaluated the impact of each campaign on child mortality rates between day 1 and 3 years of age before and after initiation each campaign.
The researchers found that mortality was lower after initiation of OPV campaigns, with a mortality rate ratio (MRR) of 0.75 (95% CI, 0.67-0.85) after campaign initiation vs. before the campaign. This trend was not reflected in other campaigns. OPV with VAS campaigns had an MRR of 1.22 (95% CI, 1.04-1.44), VAS-only campaigns had an MRR of 1.39 (95% CI, 1.2-1.61), measles vaccine campaigns with VAS had an MRR of 1.32 (95% CI, 1.09-1.6) and H1N1 campaigns had an MRR of 1.13 (95% CI, 0.86-1.49). No differences in the child mortality trend were observed between the trivalent, bivalent or monovalent OPV strains.
Aaby said that cross-protection against other infections from OPV can likely be attributed to “innate immune training rather than shared epitopes.”
“Similar studies need to be made in other countries with demographic surveillance data. WHO plans to stop OPV within the next few years,” Aaby said. “If our data are right, this could mean that childhood mortality will increase again once the children no longer get OPV.”
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