Decoding the BCG and COVID-19 connection: an empirical analysis

Abstract

Background

Bacillus Calmette-Guérin (BCG) vaccination offers protection against

tuberculosis (TB), an infectious disease caused by the Mycobacterium tuberculosis

bacterium. TB generally affects the lungs and can prove fatal. There is evidence

that BCG vaccination has non-specific immune-boosting effects that protect

against other pathogens including Candida albicans and Staphylococcus aureus.

During the early months of the COVID-19 pandemic, the list of countries most

affected bore a resemblance to the list of countries that do not have universal

BCG vaccination policy. In this study, we explore the possible association

between BCG vaccine policy and SARS CoV-2 attributable mortality.

Methods

We obtained cumulative counts of cases and deaths attributed to SARS CoV-2 from the WHO COVID-19 Dashboard,

collated details of BCG vaccination policy from the BCG World Atlas and extracted data on BCG coverage for the past

30 years from WHO. We applied multivariate log-linear regression models to examine the association of deaths per

1 million population attributed to SARS CoV-2 and BCG vaccination policy and coverage.

Results

A significant association between the absence of universal BCG vaccination and the higher death rate was found even

after controlling for other variables including median age, hospital beds and days since 100th case. The present study

does not, however, find any significant association between BCG vaccination coverage and mortality attributed to

SARS CoV-2 across the countries where the BCG immunization has been administered since or before 1990 and

where BCG coverage falls within the range 35– 99% of the population.

Conclusion

These results support the prevailing view that the connection between BCG immunization and COVID-19 mortality

is correlation rather than causation and is likely due to confounding factors within profoundly affected populations.