Coronavirus Update: Can This Century-Old Tuberculosis Vaccine Help Fight COVID-19?

Researchers are scrambling to find new ways to treat the deadly virus, including drugs and vaccines. Recently, a vaccine that is over a century old is of great interest.

The Bacillus Calmette-Guerin, a.k.a. BCG vaccine, which was designed to protect against tuberculosis, is currently under clinical trials worldwide as a way to combat the deadly novel coronavirus.

But, how can the BCG vaccine help? For starters, tuberculosis and COVID-19 are entirely two different diseases. While TB is caused by a type of bacteria, the latter is caused by a virus. However, the BCG vaccine might help build immune responses to things other than TB. It can cause certain ‘off-target effects.'

"In other words, in clinical trial format, people started picking up positive benefit from getting the vaccine that had nothing to do with tuberculosis," CNN quoted Dr. Denise Faustman, director of immunobiology at Massachusetts General Hospital and associate professor of medicine at Harvard Medical School.

The researchers are interested in studying the vaccine’s off-target effects and the way it can change the immune system in beneficial ways for autoimmune disease patients.

Although the exact mechanism of the vaccine’s off-target effects remains unclear, experts believe that the BCG vaccine could cause a nonspecific boost of the immune response.

Generally, vaccines raise immune responses to targeted pathogens, including antibodies that bind and neutralize a particular type of virus but not others. But, the BCG vaccine might increase the ability of the immune system to ward off pathogens other than the TB bacterium, according to several clinical observational studies.

A 2015 study claimed that the BCG vaccine prevents nearly 30% of infections with any known pathogen, including viruses in the first year after its administration. Also, the century-old vaccine has been proved to be relatively safe. While several countries including the U.S. haven’t been regularly administering the BCG vaccine, it has still been used widely in several developing countries throughout the world.

"I think BCG vaccine is a bit of the equivalent of a Hail Mary pass," said Schaffner. "it's such an outside-the-box concept that one would like to be optimistic, but we'll have to wait and see," CNN quoted Dr. William Schaffner, an infectious disease specialist at the Vanderbilt University School of Medicine.