a new study out of los angeles-based hospital cedars-sinai found that healthcare workers who previously received the bacillus calmette-guérin (bcg) vaccine used to prevent tb were less likely to have contracted sars-cov-2 — the virus that causes covid-19 — than workers who didn’t get the tb shot.
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dr. moshe arditi, director of the pediatric and infectious diseases and immunology division at cedars-sinai and co-senior author of the study, said in a statement that the link between the tb vaccine and likelihood of covid-19 infection was not clear, and more research is needed.
in the early 1900s, tuberculosis killed one out of every seven people living in the united states and europe, according to the centers for disease control and prevention. after discovering treatments for tb in the 1940s, scientists saw cases of the disease decrease in the united states. but numbers rose again between 1985 and 1992 as control efforts were relaxed — tb was once considered the leading cause of death in the u.s.
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the cedars-sinai team isn’t the only one looking at the use of the tb vaccine when it comes to protecting against covid-19. researchers in australia and the netherlands are also running trials to determine if bcg can help the immune system fight the virus.
the tb vaccine is researched for its “off-target” benefits, including reducing respiratory infections and sepsis , and is thought to perhaps boost the immune system . the world health organization says it is also linked to a decline in leprosy and all-cause infant mortality in certain settings.
while an inexpensive and safe vaccine, there is danger in thinking bcg is a “silver bullet” in combating covid-19 without the evidence to back it up, dr. madhukar pai, associate director at mcgill international tb centre , wrote in a forbes article . in his essay, he argued that people were wrongly connecting “bcg vaccination policies in various countries, and incidence of covid-19 cases and deaths.”
pai told healthing.ca that cedars-sinai’s new study is better than cross-country comparisons and correlations — which is when people look at countries that use bcg vaccines and the coronavirus counts and draw links between the two — but the report is still “not a direct proof that bcg will protect against covid-19.”
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what’s more, pai says that given all the vaccine success in the past month with pfizer , moderna and oxford whose vaccine results report up to 95 per cent success in preventing symptomatic covid-19, bcg may fall short even if it does offer some protection.
“i am not sure whether bcg will provide the kind of protection (about 90 per cent) seen with vaccines designed for sars-cov-2,” he says. “we have to wait and see.”