BCG Vaccine Being Studied as Potential Protection Against COVID-19

Because research has shown the Bacillus Calmette-Guérin (BCG) tuberculosis vaccine boosts production of immune cells, it is currently being trialed in people as potential protection against COVID-19.

Boosting the production of immune cells may help explain why the BCG vaccine can protect newborn babies from dying due to sepsis. In one study conducted in Perth, Australia, blood samples were analyzed from 85 newborns in Gambia, Cuinea-Bissau and Papua New Guinea, half of whom had been vaccinated. The study found newborns who had been vaccinated had about twice as many immune cells, called neutrophils, in their blood. In another study, researchers vaccinated newborn mice with BCG and then infected them with bacteria to induce sepsis. They also infected nonvaccinated mice. And, just like the babies in the other study, the mice that had been vaccinated produced double the number of neutrophils, which then protected them from dying by consuming the bacteria that cause sepsis.

“There is increasingly strong evidence that BCG, a vaccine designed to work against tuberculosis, has advantageous nonspecific effects against a range of pathogens in humans,” said Danika Hill at the Babraham Institute in Cambridge, U.K. However, Hill warns, “whether BCG, and any potential effect on neutrophils, could be beneficial against [the coronavirus] is unclear and warrants careful consideration.” According to Nelly Amenyogbe at the Telethon Kids Institute in Perth, Australia, who conducted the first study mentioned earlier, because BCG has effects on other parts of the immune system, beyond neutrophils, it is possible that these other effects may provide some benefit against COVID-19. “If vaccines such as BCG are able to provide nonspecific protection against newly emerging pathogens, this could be a game-changer for managing COVID-19 and any further pandemics,” says Hill.