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What do we know about TB vaccination offering protection against COVID-19?

Question: I’ve heard some rumblings about TB vaccination offering protection against COVID-19. What do we know?

Answer: Bacille Calmette-Guérin vaccine (BCG) is the vaccination for tuberculosis (TB) and it is offered to newborns in countries with high burden of TB. Because the US thankfully does not have a high burden of TB, the BCG vaccine is not commonly given here. A couple of ecological studies recently came out highlighting that countries that have high BCG vaccination rates do not seem to have high COVID-19 infection or mortality rates. On the heels of theses studies, WHO issued some guidance on this topic, stating “There is no evidence that the BCG vaccine protects people against infection with COVID-19 virus.” For ease of reference, I’ve synthesized the main points of the WHO guidance here. In short, there’s still a LOT we don’t know, but scientists are actively working to fill our knowledge gaps. In the meantime, BCG vaccination should be reserved for newborns in countries with high TB burden as BCG vaccination itself is in relatively short supply globally.

  • While there’s some experimental evidence from animal and human studies that BCG vaccine has some effects on the immune system, the clinical relevance of these effects is unknown.
  • As of 11 April, there are three pre-print manuscripts (e.g. not yet peer reviewed) that show COVID-19 prevalence is lower in countries with widespread BCG use compared with others. These types of ecological studies are prone to bias and are quite weak. We cannot rely on these findings as evidence to inform programs or policies. Instead, such findings call for more rigorous research.
  • Rigorous research is happening with two registered clinical trials actively recruiting to explore impact of BCG vaccination given to health workers involved in the care of COVID patients.
  • From Lancet article cited in WHO guidance, “Due to problems with vaccine production and limited supplier options in some countries, the global availability and procurement of BCG has been a challenge since 2013.”
  • WHO’s current recommendation is: “BCG vaccination prevents severe forms of tuberculosis in children and diversion of local supplies may result in neonates not being vaccinated, resulting in an increase of disease and deaths from tuberculosis. In the absence of evidence, WHO does not recommend BCG vaccination for the prevention of COVID-19. WHO continues to recommend neonatal BCG vaccination in countries or settings with a high incidence of tuberculosis.”