How a 100-year-old TB vaccine could help fight Covid-19

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Tuberculosis and Covid-19 infection are two very different diseases – tuberculosis is caused by a type of bacteria while Covid-19 is caused by a virus, to begin with. But the BCG vaccine could help people develop immune responses to things other than tuberculosis, causing “off-target effects,” according to Dr. Denise Faustman, director of immunobiology at Massachusetts General Hospital and associate professor of medicine at Harvard Medical School.

“In other words, in clinical trials, people started to gain positive benefits from receiving the vaccine which had nothing to do with tuberculosis,” she said. Faustman has studied how the BCG vaccine has affected people with type 1 diabetes for many years. She is interested in how its off-target effects modify the immune system in a way that benefits people with autoimmune diseases such as type 1 diabetes.

There is currently no U.S. Food and Drug Administration-approved vaccine or treatment for the new coronavirus. While hoping that the BCG vaccine will prove effective against Covid-19 – as with all treatments and vaccines under development – Dr William Schaffner, infectious disease specialist at Vanderbilt University School of Medicine, admits that the concept is a unconventional.

“I think the BCG vaccine is kind of like a pass, ‘Hail Mary,'” said Schaffner. “It is such an original concept that we would like to be optimistic, but we will have to wait and see. “

Several countries around the world are starting human clinical trials to assess the effectiveness of the BCG vaccine, such as Australia and the Netherlands.

Faustman and his colleagues are preparing for tests in Boston, which are currently undergoing a multi-step review process. Once approved, she and her team members hope to enroll approximately 4,000 health care workers in the trial.

The vaccine has been available for over 100 years and has been shown to be relatively safe, said Faustman.

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“BCG is announced by the World Health Organization as the safest vaccine ever developed in the world,” she said. “More than 3 billion people have obtained it. “

Although several countries, including the United States, do not regularly administer the BCG vaccine, it is still widely used in developing countries.

Researchers have attempted to determine whether these countries that regularly administer the BCG vaccine have lower Covid-19 mortality rates. A study by researchers in New York found an association between universal BCG vaccination policies in countries and reduced morbidity and mortality for Covid-19. The study was not peer reviewed or published in a medical journal.

But why has China experienced high morbidity and mortality with Covid-19 despite a universal BCG policy since the 1950s? The study said China had a weakened policy during the Cultural Revolution in the 1960s and 1970s, which could have created “a pool of potential hosts who would be affected by and spread COVID-19. “

In addition, China has not experienced such a sharp increase in its curve compared to some other countries without universal policies, such as Italy, Spain and the United States, said Faustman. She also added that different strains of the BCG vaccine may have different efficacy rates.

One of the main limitations of the study is that it compares data from different countries, which have different timelines for Covid-19 and different capabilities to test.

“This was a 30,000-foot comparison of the frequency of Covid-19 infections in countries that used the BCG vaccine extensively and those that did not,” said Schaffner of Vanderbilt. “We should not draw conclusions from it because … the countries are very different. And so there can be many other reasons that determine how often Covid has performed in these countries.

“The study provides additional encouragement for more specific investigations, such as the clinical trials that will take place. “

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