Biology / Health / Medicine / Microbiology / Science

An unexpected bonus

I’ve been steering clear of covering the COVID-19 pandemic, as described in an earlier post, but I couldn’t resist sharing some news about an old friend of mine. It turns out that the BCG (Bacillus Calmette-Guérin) vaccine may be good for more than just protection against infection by Mycobacterium tuberculosis. How’d we figure that out?

Well, a non-peer reviewed study has taken a look at data for deaths caused by SARS-CoV-2 in various countries and compared it to their vaccination policies. Those who routinely administer the BCG vaccine seem to have both lower mortality (i.e. lower death rates) and lower morbidity (less serious disease) with the coronavirus. This is a trial just looking at existing data, though, and actual clinical trials have yet to be launched.

Is there any chance it works? It’s easy to deride the idea: tuberculosis is a bacterium, and SARS-CoV-2 a virus. It doesn’t seem like a vaccination for tuberculosis could possibly target a coronavirus at all. It sounds silly!


It isn’t! BCG vaccination is thought to stimulate the immune system. We do have convincing data from a proper randomised controlled trial which found that vaccinated newborns were forty percent less likely to die from respiratory diseases than unvaccinated peers. That’s a pretty huge effect, and it’s not that the children are being protected just from tuberculosis (though it’s true TB is still a threat in West Africa, where the trials took place) — this effect held for all respiratory diseases.

What’s more, the BCG is actually used to treat people with certain bladder cancers… and this isn’t a niche treatment, it’s a key part of the arsenal. It’s considered an immunotherapy drug!

So it’s not as bonkers as it sounds… but don’t go rushing for a BCG vaccination yet. Clinical trials need to happen, and even if it has a protective effect by stimulating the immune system, that’s no guarantee you won’t get (and spread) respiratory viruses. It may prove to be an important tool, but we don’t know yet.

(In general, though? Get a tuberculosis vaccination. Tuberculosis is nasty and, contrary to popular belief, it ain’t dead yet.)

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