Could a Century-Old TB Shot Protect Against Other Respiratory Diseases?

Could a Century-Old TB Shot Protect Against Other Respiratory Diseases? A trial in Greece shows a long-used tuberculosis vaccine may cut respiratory infections, raising hopes for similar protection against Covid-19. Gayathri Vaidyanathan Wired

Three years ago, doctors in Greece began recruiting 198 older people for a unique experiment. They injected half of them with a century-old tuberculosis vaccine typically given to newborns in the developing world. They gave the other half a placebo. They wanted to find out if the vaccine, called Bacillus Calmette–Guérin, or BCG, would protect older people—not against TB, but more broadly against viral infections.

Results are now in: During the year after receiving the shot, the BCG group had 80 percent fewer serious respiratory viral infections than the unvaccinated group. The results were published in Cell at the end of August by doctors at the University of Athens Medical School in Greece, and Radboud University Medical Centre in Nijmegen, Netherlands.

That’s a big deal for a few reasons. People 65 years and older are more likely than any other age group to be hospitalized due to respiratory infections such as influenza, and this study is a preliminary signal that some vaccines could have broad beneficial effects beyond protection from a particular disease. And Covid-19, too, is a respiratory viral illness that disproportionately leads to the hospitalization of older people.

“The chances are increased that BCG would have the same effect on Covid-19 as on other viral respiratory infections like the flu,” says Mihai Netea, the senior author of the study and experimental internal medicine chair at Radboud University. Tests of whether BCG specifically protects against Covid-19 are ongoing; there are now at least 20 randomized clinical trials around the world to see whether it can indeed protect health workers and the elderly.

Many scientists now believe that BCG and some vaccines like it that contain a live, weakened virus may act against non-target diseases. A 2016 review commissioned by the World Health Organization found that BCG and the measles vaccines reduce overall mortality by “more than would be expected through their effects on the diseases they prevent.”

“I think that we have to acknowledge that vaccines have effects much broader than the target disease and the effects can be used,” Netea says. ...