Can an Old Vaccine Stop the New Coronavirus?

The scientists cultured bacterial scrapings from cow udders, and continued to culture bovine TB for over a decade until it was weak enough that it no longer caused virulent disease when given to lab animals.

The weakened virus was first used in humans in 1921 and was widely adopted after World War II. Now B.C.G. is primarily used in the developing world and in countries where TB is still prevalent, where it is given to over 100 million babies a year.

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Like other vaccines, B.C.G. has a specific target: TB. But evidence accumulating over the past decade suggests the vaccine also has so-called off-target effects, reducing viral illnesses, respiratory infections and sepsis, and appears to bolster the body’s immune system.

The idea is an offshoot of the “hygiene hypothesis,” which suggests that the modern emphasis on cleanliness has deprived children of exposure to germs. The lack of “training” has resulted in weakened immune systems, less able to resist disease.

One of the earliest studies hinting at the broad benefits of B.C.G. vaccination was a randomized trial of 2,320 babies in Guinea-Bissau in West Africa, published in 2011, that reported that death rates among low-birth-weight babies were dramatically reduced after vaccination. A follow-up trial reported that infectious-disease mortality rates in low-birth-weight babies who were vaccinated were cut by more than 40 percent.

Other epidemiological studies — including a 25-year study of over 150,000 children in 33 countries — have reported a 40 percent lower risk of acute lower respiratory tract infections in children who received a B.C.G. vaccine.

Article source: https://www.nytimes.com/2020/04/03/health/coronavirus-bcg-vaccine.html