A Systematic Review of BCG and tie-in to coronavirus disease: A Point of Contention for Global Health?

Background: COVID-19, a pandemic that started in December 2019 from the city of Wuhan in China. BCG (Mycobacterium Bovis Bacillus Calmette-Guérin) is a live attenuated vaccine used for tuberculosis (TB) that. The BCG vaccine became a part of the ‘National Tuberculosis Control Program (NTCP)’ in India in 1962. The BCG vaccine is given to all children in India, preferably within the first year after birth. However, as per CDC recommendations in the US, BCG is only considered for very select cases, for e.g. children who have a negative TB test and who are continually exposure to adults with TB disease. It induces epigenetic and metabolic alterations at promoter sites of genes encoding inflammatory cytokines such as IL-1,IL-6 and TNF that improve the innate immune response to the subsequent infections by trained immunity. This may be useful in management of COVID-19. Method: We conducted a literature review searching databases like Cochrane, PubMed, Google scholars, CINAHL, LILACS, UpToDate, Scopus, EMBASE, WOS, and Science Direct. We used the following keywords: COVID 19, SARSCoV2 and BCG vaccines. We included case reports, case series and cohort (retrospective and prospective). Results: The global trend suggested an inverse association between BCG vaccination policy and COVID-19 mortality. Countries with current BCG vaccination had lower deaths and was negatively associated with COVID-19 deaths per million Patients with BCG vaccination were more likely to experience myalgia and less likely to require hospital admission. BCG is known to elicit non-specific immune effects through the induction of the innate immune responses and the enhanced production of IL-1β and help combat COVID-19 like respiratory infections. Conclusion: If the BCG vaccine is proven to provide non-specific protection to bridge the gap before a diseasespecific vaccine is developed, this would be an important tool in the response to COVID-19 and future pandemics.