Scientists are testing old vaccines against other germs to see if they could provide a little stopgap protection against COVID-19 until a more precise shot arrives.
Vaccines are designed to target a specific disease. But vaccines made using live strains of bacteria or viruses seem to boost the immune system’s first line of defense, a more general way to guard against germs. And history books show that sometimes translates into at least some cross-protection against other, completely different bugs.
There’s no evidence yet that the approach would rev up the immune system enough to matter against the new Coronavirus. But given that a brand-new vaccine is expected to take 12 to 18 months, some researchers say it’s time to put this approach to a faster test, starting with a tuberculosis vaccine.
“This is still a hypothesis,” said Dr. Mihai Netea of Radboud University Medical Center in the Netherlands. But if it works, “it could be a very important tool to bridge this dangerous period until we have on the market a proper, specific vaccine.”
The World Health Organization issued a stern warning Monday not to use the TB vaccine against COVD-19, unless and until studies prove it works.
Already nearly 1,500 Dutch health care workers have rolled up their sleeves for one study that Netea’s team is leading. It uses that TB vaccine, named BCG, which is made of a live but weakened bacterial cousin of the TB germ.
In Australia, researchers hope to enroll 4,000 hospital workers to test BCG, too, and 700 already have received either the TB vaccine or a dummy shot. Similar research is being planned in other countries, including the U.S.
Possibly next in line: Oral polio vaccine, drops made of live but weakened polio viruses. The Baltimore-based Global Virus Network hopes to begin similar studies with that vaccine and is in talks with health authorities, network co-founder Dr. Robert Gallo told The Associated Press.
Rapid studies are needed to tell if there could be “long-ranging effects for any second wave of this,” said Gallo, who directs the Institute of Human Virology at the University of Maryland School of Medicine.
At the U.S. National Institutes of Health, researchers are in early discussions about proposals to study the TB and polio vaccines as a possible COVID-19 defense.
There’s a big caution: Live vaccines are risky for people with weakened immune systems, and shouldn’t be tried against COVID-19 outside of a research trial.
There are overlapping types of immune defenses. The usual goal of a vaccine is to prime the body to recognize a specific health threat and make antibodies able to fight back when that particular bug comes along.
But that takes time. So at the first sign of infection, a first line of foot soldiers — white blood cells — springs into action to fend off the invader in other ways, what’s called innate immunity. If they fail, then the body creates its more targeted special forces to join the fight.
Scientists not involved in the effort to try these vaccines against COVID-19 say it’s worthwhile to test.
