Does Bacille Calmette-Guérin Vaccination Provides Protection against COVID-19: A Systematic Review and Meta-analysis

Area of Science:

• Immunology
• Infectious Diseases
• Public Health

Background:

• Geographic variations in SARS-CoV-2 morbidity and mortality have been linked to historical Bacille Calmette-Guérin (BCG) vaccination policies.
• The potential protective effect of BCG vaccination against COVID-19 in adults requires systematic evaluation, considering confounding factors like disease burden and population density.

Purpose of the Study:

• To systematically evaluate and correlate the effect of Bacille Calmette-Guérin (BCG) vaccination on COVID-19 outcomes.
• To investigate whether long-standing BCG vaccination policies are associated with better prognosis in adults affected by SARS-CoV-2.

Main Methods:

• A comprehensive electronic search was conducted for randomized controlled trials (RCTs) and observational studies.
• Databases searched included PubMed, Cochrane Library, and ClinicalTrials.gov.
• Twenty-eight observational studies were included in the final analysis after an initial yield of 114 studies.

Main Results:

• Analysis of 28 observational studies suggests that BCG vaccination is associated with a decrease in COVID-19 incidence and mortality.
• These findings indicate a potential protective effect of BCG vaccination against SARS-CoV-2.
• Caution is advised when interpreting these results due to the presence of numerous confounding factors within the included studies.

Conclusions:

• The hypothesis that BCG vaccination offers protection against COVID-19 is supported by evidence from multiple studies and cannot be dismissed.
• Further strengthening of this evidence base requires well-conducted randomized controlled trials (RCTs) and observational studies.
• The potential role of BCG vaccination in mitigating COVID-19 requires continued investigation.