Exercising caution in correlating COVID-19 incidence and mortality rates with BCG vaccination policies due to variable rates of SARS CoV-2 testing

Janine Hensel; Daniel J McGrail; Kathleen M McAndrews; Dara Dowlatshahi; Valerie S LeBleu; Raghu Kalluri

Since the early 1920s, the use of the Bacillus Calmette-Guerin (BCG) vaccine has been implemented in several countries to prevent tuberculosis (TB), a disease caused by Mycobacterium tuberculosis. Infection with Mycobacterium tuberculosis primarily impacts lung function, and may lead to TB-related death. The vaccine consists in exposure to the M. tuberculosis-related, live, attenuated Mycobacterium bovis strain. The BCG vaccine thus offers a partial and possibly variable immunity against TB, and its off-target effect has also been linked to protection against other infectious diseases [1] . There is evidence from previous outbreak that supports the hypothesis that BCG vaccination can protect against RNA and DNA viral infections (herpes and influenza) and other disease such as asthma [2, 3] . These observations have given support to the possibility of the BCG vaccine providing protection against infection with the novel coronavirus, SARS CoV-2 (CoV-2). CoV-2 infection results in the disease known as COVID-19, which is associated with fever and severe respiratory illness. The WHO declared COVID-19 a pandemic on March 11 th 2020. As of April 7 th , 2020, 81 countries around the globe reported over 500 COVID-19 cases.