Previous BCG vaccination is associated with less severe clinical progression of COVID-19

1. In this case-control study, previous BCG vaccination was associated with a reduced risk of developing severe COVID illness for those who are not vaccinated against COVID-19. 

Evidence rating level: 3 (Average)

The Bacillus Calmette-Guerin (BCG) vaccine for tuberculosis is known to have non-specific effects, including protection against respiratory viruses such as RSV. Recommendations for BCG vaccination are made based on the regional incidence of TB. This case-control study aimed to assess whether previous BCG vaccination offers protection against severe covid illness. The study included individuals who presented to COVID-19 referral care units in Salvador, Sao Paulo, and Recife in Brazil, excluding those vaccinated for COVID-19. Individuals who were hospitalized in ICU with severe COVID-19 (497 cases) were compared to those, who were individuals with COVID-19 who presented to the same health units and were not hospitalized or were hospitalized in general wards (670 controls). Data collection occurred from 2020 to 2021. Compared to controls, those with severe COVID-19 were significantly more likely to be above 60 years of age, have higher education, and have at least one comorbidity, with p <0.000. The control group was significantly more likely to have previous BCG vaccination (58.7% of the severe COVID-19 group, compared to 92.1% of controls), with p <0.000. After adjusting for race, education level, sex, age, municipality, and presence of comorbidity, the odds ratio was 0.27 (95% CI 0.17–0.44), demonstrating a protective effect from BCG vaccination of 73% (95% CI: 56.0–83.0%). The protective effect conferred by BCG vaccination was reduced in the 60+ age group, at 35% (95% CI 33-71%). This research suggests that the non-specific effects of BCG vaccination offer protection against severe COVID-19 illness. Future research may examine whether the BCG vaccine confers a benefit to those who are also immunized for COVID-19. 

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