BCG Vaccination Policy and Protection Against COVID-19: Correspondence
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CORRESPONDENCE
BCG Vaccination Policy and Protection Against COVID-19: Correspondence
To the Editor: Meena and colleagues [1] have opined about the recent study [2] which failed to show the protective effect of Bacillus Calmette-Guérin (BCG) vaccine. The quoted study showed no difference in the rate of infection between BCG vaccinated and non-vaccinated young adults, also did not find difference in severity of COVID-19 among above two groups [2]. We discuss the available important scientific evidences those are in favour of BCG’s protective efficacy in severity reduction of COVID-19. Recent analysis has shown proportionately less cases, milder illness and a lower death rate due to COVID-19 in BCG vaccinated population as compared to BCG nonvaccinated across countries and hemispheres [3]. Two separate multi-centre placebo-controlled parallel group randomized trials are ongoing in response to COVID-19 in the Netherlands and Australia to assess whether BCGDanish vaccine reduces healthcare workers’ absenteeism and hospital admission among the elderly during the COVID-19 pandemic [4]. These trials are ‘BCG vaccination to protect healthcare workers against COVID-19’ (BRACE) and, ‘Reducing healthcare workers absenteeism in COVID-19 pandemic through BCG vaccine (BCG-CORONA)’ [4]. The above ongoing trials are based on the concept of protection from COVID-19 due to immunity induced by BCG vaccination. BCG vaccination alters a secondary innate immune response upon viral infection resulting in improved antiviral responses and lowering viremia [5]. The BCG vaccine has shown to reduce the severity of infections caused by structurally similar singlestranded positive-sense RNA virus like SARS-CoV-2 is, in controlled trials. For example, in healthy human volunteers, the BCG vaccine has reduced Yellow fever vaccine induced viremia by 71% (95% CI: 6–91) which was induced by live attenuated Yellow fever vaccine, in the study performed in Netherlands [5]. The people of the TB endemic countries like India seem to have some protection in terms of severity and deaths in comparison to TB non-endemic countries (like Europe and USA) etc. where BCG vaccination is not given. It appears that the immunity might be unable to stop COVID-19 infection, but is likely to diminish its virulence on selective individuals.
Better understanding of the molecular mechanisms is still evolving. Identifying the factors that impact the non-specific effects of BCG, could be a clue towards novel therapeutic options for reduction of severe morbidity and mortality associated with COVID-19. Prasanta Raghab Mohapatra1 and Baijayantimala Mishra2 Department of 1 Pulmonary Medicine & Critical Care, and 2 Microbiology, AII India Institute of Medical Sciences, Bhubaneswar, India. E-mail: [email protected]
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Meena J, Yadav A, Kumar J. BCG vaccination policy and protection against COVID-19. Indian J Pediatr. 2020. https://doi.org/10.1007/ s12098-020-03371-3. Hamiel U, Kozer E, Youngster I. SARS-CoV-2 rates in BCG-vaccinated and unvaccina
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