A shred of evidence that BCG vaccine may protect against COVID-19: Comparing cohorts in Spain and Italy

Introduction There is evidence that the BCG vaccine against tuberculosis also helps prevent other diseases – perhaps including COVD-19. Spain had a program for universal BCG vaccination until 1981. Objective To see whether cohorts born when Spain had a program of universal BCG vaccination had lower rates of confirmed cases of COVID-19 and mortality (relative to similar cohorts in Italy). Methods We compare COVID-19 mortality and confirmed cases for those born roughly a decade before and after 1981. We compare the outcomes to the same age cohorts in Italy, which never had universal BCG vaccination. Results The Spanish cohort that received BCG had a relative risk of 0.962 of having a confirmed case of COVID-19. This risk is statistically significantly below unity (95% CI 0.952 to 0.972, P< 0.001). There is also suggestive evidence the BCG cohort in Spain had lower mortality (relative risk 0.929, CI 0.850 to 1.01, P = 0.11). The small sample size makes this test underpowered. Conclusion These suggestive results provide a shred of evidence that BCG vaccinations help protect against COVID. I outline many limitations to this study and point how better data can help be more convincing.