The Impact of Bacillus Calmette-Guérin (BCG) Revaccination on COVID-19 Infection Among Healthcare Workers: A Systematic Review and Meta-Analysis

The Bacillus Calmette-Guérin (BCG) vaccine has been hypothesized to confer nonspecific immune protection against viral infections, including coronavirus disease 2019 (COVID-19). This meta-analysis evaluates the protective role of BCG vaccination in preventing COVID-19 among healthcare workers (HCWs). A systematic review and meta-analysis were conducted of randomized controlled trials (RCTs) that reported the effect of BCG vaccination for COVID-19 prevention in HCWs compared with placebo. Nine RCTs were included, with a total of 10,295 HCWs. Pooled odds ratios (ORs) and mean differences (MDs) were calculated using random- and fixed-effects models to assess the impact on symptomatic COVID-19, severe disease, hospitalization, seropositivity, duration of illness, and serious adverse events. Heterogeneity was evaluated using I² statistics. BCG vaccination did not significantly reduce the risk of symptomatic COVID-19 (OR = 1.05, 95% CI: 0.94-1.17, p = 0.43, I² = 47%), severe COVID-19 (OR = 1.20, 95% CI: 0.97-1.48, p = 0.09, I² = 0%), or hospitalization (OR = 1.04, 95% CI: 0.71-1.50, p = 0.86, I² = 0%). There was no significant difference in the duration of symptomatic illness (MD = 0.09 days, 95% CI: -1.41-1.59, p = 0.90, I² = 80%) or in rates of COVID-19 seropositivity (OR = 1.27, 95% CI: 0.81-1.98, p = 0.30, I² = 76%). The incidence of serious adverse events was not significantly different between groups (OR = 1.43, 95% CI: 0.34-5.97, p = 0.62, I² = 81%). This meta-analysis found no significant protective effect of BCG vaccination against any clinical or serological endpoint of COVID-19 in HCWs. The results do not support the use of BCG as a preventive measure against COVID-19 in this population.