Emerging research suggests that using the tuberculosis vaccine Bacillus Calmette-Guerin (BCG) can help in fighting the coronavirus infection.

It is known that the countries where there was mandatory BCG vaccination, had less mortality from COVID-19. This only suggests that BCG, in general, can boost people's immunity and so help in fighting the novel coronavirus.

Even the World Health Organization (WHO) has cautioned against using BCG vaccine until more is known about its effects on the coronavirus.

Fair Comparision

Researchers from Virginia Polytechnic Institute used existing data to find if countries without a national BCG vaccination program had greater COVID-19 mortality rates. They undertook to compare it fairly and accounted for factors such as population density, access to healthcare and the coronavirus response.

Vaccine Human Trial
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Luis Escobar and his colleagues from the institute found a strong link between BCG vaccination use and lowered COVID-19 mortality rates across socially similar European countries. For every 10 percent increase in the BCG index, associated with the degree of universal BCG vaccination was linked with a 10.4 percent reduction in COVID-19 mortality, according to the paper published in the journal Proceedings of the National Academy of Sciences.

Carolina Barillas-Mury, who is a distinguished investigator with the National Institutes of Health told CNN that the researchers 'very carefully' removed variables. "When we removed them, if this was not true, the association should have disappeared. Instead of disappearing, it became stronger and stronger -- more straightforward," she added.

The paper also discusses the innate immune response of the body, "to adapt and 'learn' from previous exposure to a pathogen," calling it an "ancient response," as it is observed in organisms such as plants, insects, along with humans.

It is called "trained immunity," defined as the enhancement in innate immune responses to subsequent infections, such that the immune cells are programmed to mount a stronger response to pathogens and to activate adaptive responses more efficiently, as previously reported.

Trained immunity confers broad protection and is not pathogen-specific. For instance, BCG vaccination is an approved treatment for bladder cancer, as it aids in the destruction of cancer cells, mediated by trained immunity

Broad Spectrum Immunity

However, this was not enough to establish causality with the 100-year-old BCG vaccine, according to the paper. Scientists call for clinical trials. But there is a strong evidence suggesting that the vaccine provides nonspecific or broad spectrum immunity beyond tuberculosis.

Coronavirus
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BCG's efficacy has been inconsistent in adults with TB. Some researchers also say that vaccines for polio and measles, mumps and rubella, provide similar immunity against lethal infections, including the coronavirus.

Bill and Melinda Gates Foundation granted $10 million in May for the clinical trials in Australia, Spain, and The Netherlands that includes 10,000 health care workers.

Dr. Denise Faustman, director of immunobiology at Massachusetts General Hospital might soon begin BCG trials in Boston. For many years she has been studying the off-target effects of the BCG vaccine.

Infections Can be Fought Faster

"BCG boosts the innate immune system," added Faustman. An infectious disease can be fought off faster, she said. The BCG vaccine could possibly boost the efficacy of a coronavirus-specific vaccine, once its created, Faustman believes as it would have significant public health implications.

Once the trials are done with a positive result, the vaccine could be administered in countries not having a mandatory universal vaccination program, like the US.

However, Dr. William Schaffner, an infectious disease specialist from Vanderbilt University School of Medicine cautioned about observational data from many countries as they do not assess coronavirus cases and deaths the same way.