While the vaccine, used in many low- and middle-income countries, isn’t considered to be highly effective against its primary goal, TB, it seems to help the immune system fend off various pathogens, including one that causes leprosy. The question is whether the virus known as SARS-CoV-2 is among them.

Not everyone is convinced.

A leading TB researcher, Madhukar Pai, has warned that the BCG vaccine is unlikely to be the magic bullet some people seem to think it may be. Pai, director of McGill University’s International TB Center, wrote a blog post over the weekend arguing that people may be ascribing almost magical powers to the vaccine.

“I think the idea is 100% worth investigating,” Pai said in an interview with STAT. “That’s why my piece was not against further research. My piece was saying: Right now we’re nowhere close to anything for a policy based on ecological studies that are full of holes.”