It has been observed that countries without universal policies of BCG vaccination are more severely affected compared to countries with long-established BCG vaccination policies. This has led researchers to investigate the possible relation between BCG and COVID-19. The authors have evaluated the current research regarding the role of the universal Bacille Calmette Guerin (BCG) vaccination policy of a country to the morbidity and mortality due to COVID-19/ SARS-CoV-2 in that country. It is believed that the BCG vaccine trains the immune system of the human body for non-mycobacterial pathogens through non-specific immunotherapeutic mechanisms. Most of the epidemiological studies point towards a positive correlation but barring a few, and they tend to ignore factors like lower testing rates in countries having universal BCG policy. BCG vaccination policy cannot be seen in isolation as the factors like climatic conditions, nutritional habits, genetic and ethnic aspects, social and cultural influence and age distribution also are responsible for the varied morbidity and mortality due to COVID-19. Multiple-dose BCG vaccine repurposing for SARS-CoV-2, however, should be explored. Clinical trials of the BCG vaccine to test its efficacy on SARS-CoV-2 are urgently needed before deducing unidirectional correlations.
Key words: SARS-CoV-2; Universal BCG vaccination policy; COVID-19; Coronavirus; Morbidity; Mortality
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