Why It Matters | Does the BCG vaccine prevent Covid-19? No, says study.

The BCG vaccine was found to not protect against Covid-19 among healthcare workers

The BCG vaccine administered to prevent tuberculosis didn’t provide any significant protection against Covid-19 to healthcare workers. Representative image. | Photo Credit: Ramalingam B. Jothi/The Hindu

What are the facts: The BCG vaccine, typically administered to prevent tuberculosis, did not provide any significant protection against Covid-19 infection to healthcare workers, a new study said. Published in the New England Journal of Medicine, the study’s results stated that 14.7% of the participants who received the bacillus Calmette-Guerin (BCG) vaccine showed symptoms of Covid-19 infection. In comparison, 12.3% of the participants in the placebo group showed signs of Covid-19 infection. Five participants from each group were hospitalised due to Covid-19 and one participant from the placebo group succumbed to the infection.

What is the context?

• The clinical trial to repurpose the BCG vaccine against Covid-19 started during the early days of the pandemic when there were fewer ways to treat Covid-19.
• The BCG vaccine has existed for over 80 years and is part of India’s Universal Immunisation Programme.
• The vaccine, containing weakened strains of Mycobacterium tuberculosis, is administered to fight against tuberculosis, meningitis and other respiratory tract infections, according to another study.
• The current study was supposed to have 10,000 participants from five countries and continue for 12 months, but was stopped once mRNA vaccines were developed.
• The paper reported the results of a trial where 4,000 adults were observed over six months. 

Why does it matter?

• While the study proved that the BCG vaccine “did not reduce the risk of Covid-19”, it would be unwise to discard the effects of the vaccine in other instances, scientists said. 
• “The conclusion of our trial — that B.C.G. does not protect health care workers against mild or moderate Covid — is true,” Dr. Nigel Curtis, the trial’s principal investigator, told The New York Times.
• “This doesn’t tell us anything about the ability to protect people in other age groups against infections. BCG is still a very important concept in infants,” he added. 
• He also noted that analysis from the data collected during the trial is still going on and that the vaccine’s effects may change depending on the virus or bacterium to which it’s exposed.