As scientists around the globe rushed to create vaccines for COVID-19, Cedars-Sinai investigators also looked back in time for ways to shield people from the disease. They found one potential avenue in bacille Calmette-Guerin (BCG), a vaccine developed a century ago to battle tuberculosis.

More than 100 million children worldwide receive the BCG shot each year, and the vaccine also has longstanding approval from the Food and Drug Administration as a treatment for bladder cancer. Several studies are currently investigating if BCG vaccination can provide protection against severe SARS-CoV2 infection.

To gauge its potential for stopping COVID-19 infection, researchers tested the blood of more than 6,000 healthcare workers in the Cedars-Sinai Health System. Participants were also asked about their medical and vaccination histories.

The study found that those with a history of BCG vaccination—about 30% of the total—were significantly less likely to have tested positive for COVID-19 antibodies than those who had never received the BCG vaccine. They were also less likely to report related symptoms. Similar effects were not shown in those who had only been immunized against the flu, meningitis or pneumonia.

"It appears that BCG-vaccinated individuals either may have been less sick or they may have mounted a more efficient cellular immune response against the virus," says Moshe Arditi, MD, executive vice chair for Research in the Department of Pediatrics, director of the Division of Pediatric Infectious Diseases, and the GUESS?/Fashion Industries Guild Chair in Community Child Health.

While noting that BCG would not be more effective than the vaccines developed specifically for COVID-19, he calls it "a potentially important bridge that could offer some benefit" in certain countries before the approved COVID-19 vaccines are available for all.

"It would be wonderful if one of the oldest vaccines that we have could help defeat the world’s newest pandemic," Arditi says.

In the Newsroom: Study: TB Vaccine Linked to Lower Risk of Contracting COVID-19