BCG vaccination in health care providers and the protection against COVID-19

A number of coronavirus disease 2019 (COVID-19) vaccine candidates have shown promising results, but substantial uncertainty remains regarding their effectiveness and global rollout. Boosting innate immunity with bacillus Calmette Guerin (BCG) or other live attenuated vaccines may also play a role in the fight against the COVID-19 pandemic. BCG has long been known for its nonspecific beneficial effects that are most likely explained by epigenetic and metabolic reprogramming of innate immune cells, termed trained immunity. In this issue of the JCI, Rivas et al. add to these arguments by showing that BCG-vaccinated health care providers from a Los Angeles health care organization had lower rates of COVID-19 diagnoses and seropositivity compared with unvaccinated individuals. Prospective clinical trials are thus warranted to explore the effects of BCG vaccination in COVID-19. We posit that beyond COVID-19, vaccines such as BCG that elicit trained immunity may mitigate the impact of emerging pathogens in future pandemics.

Automated summary

Several COVID-19 vaccine candidates have shown promise, but uncertainty remains about their effectiveness and global distribution. Boosting innate immunity with vaccines like BCG may play a role in combating COVID-19, as evidenced by lower infection and seropositivity rates in BCG-vaccinated individuals. Further clinical trials are needed to explore the potential of BCG vaccination in COVID-19 and future pandemics.