Melinda Wenner Moyer writes:

As the world waits for a coronavirus vaccine, tens of thousands of people could die. But some scientists believe a vaccine might already exist.

Surprising new research in a niche area of immunology suggests that certain live vaccines that have been around for decades could, possibly, protect against the coronavirus. The theory is that these vaccines could make people less likely to experience serious symptoms — or even any symptoms — if they catch it.

At more than 25 universities and clinical centers around the world, researchers have begun clinical trials, primarily in health care workers, to test whether a live tuberculosis vaccine that has been in use for 99 years called the bacillus Calmette-Guérin, or B.C.G., vaccine, could reduce the risks associated with the coronavirus.

Another small but esteemed group of scientists is raising money to test the potential protective effects of a 60-year-old live polio vaccine called O.P.V.

It’s counterintuitive to think that old vaccines created to fight very different pathogens could defend against the coronavirus. The idea is controversial in part because it challenges the dogma about how vaccines work.

But scientists’ understanding of an arm of immunology known as innate immunity has shifted in recent years. A growing body of research suggests that live vaccines, which are made from living but attenuated pathogens (as opposed to inactivated vaccines, which use dead pathogens) provide broad protection against infections in ways that no one anticipated. [Continue reading…]