The BCG vaccine, a vaccine originally made against tuberculosis, has a general stimulating effect on the immune system and is therefore effective against multiple infectious diseases—possibly also against COVID-19. This study compared groups of volunteers who have received a BCG vaccine (or not) in the past five years (before the corona pandemic), showing that the vaccine is safe and possibly influences COVID-19 symptoms.

Not only the acquired immune system but also the innate immune system has a memory. And the BCG vaccine against tuberculosis can stimulate this memory. After a BCG vaccination the innate immune system responds better to a wide range of other infections. Mihai Netea and colleagues from Radboud university medical center discovered and described how that works. They think that the old vaccine could be useful for specific target groups, such as the elderly.