OPV as Potential Protection Against COVID-19

Since the 1960s, studies have shown that oral polio vaccine (OPV) may have beneficial non-specific effects, reducing morbidity and mortality from other infections than polio. Such beneficial non-specific effect have been observed for other live vaccines, including measles, smallpox and BCG vaccine. For BCG, the vaccine for which the mechanism has been studied the most, the effects appear to be mediated through the innate immune system. The COVID-19 pandemic caused by the novel coronavirus SARS-CoV-2 has now caused over 7.1 million cases and >400,000 deaths worldwide. As everywhere else, it is anticipated that in Africa the older part of the population will be at risk of severe COVID-19. OPV is widely used in Africa, but for children. Both polio and coronavirus are positive-strand RNA viruses, therefore it is likely that they may induce and be affected by common innate immune mechanisms. In a randomised trial at the Bandim Health Project in Guinea-Bissau, the investigators will assess the effect of providing OPV vs no vaccine to 3400 persons above 50 years of age. The trial will have the power to test the hypothesis that OPV reduces the combined risk of morbidity admission or death (composite outcome) by at least 28% over the subsequent 6 months.