Efficacy of BCG Vaccination Against COVID-19 in Older Adults

Background: The Bacillus Calmette-Guérin (BCG) vaccine has been considered a potential preventive measure against coronavirus disease 2019 (COVID-19). However, no systematic review or meta-analysis has specifically evaluated its effects on COVID-19 outcomes in older adults. Therefore, our study examined the impact of BCG vaccination on the severity and mortality of COVID-19 in this population. Methods: A systematic search of PubMed, Embase, and the Cochrane Library was conducted for studies published up to December 31, 2024. Among 458 studies identified, 5 randomized controlled trials (RCTs) met the inclusion criteria. Results: All 5 studies were placebo-controlled RCTs conducted in Europe and published between 2022 and 2024, involving a total of 12,128 participants. There were no significant differences in documented severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (RR: 1.05, 95% CI: 0.91-1.22), COVID-19-related hospitalization (RR: 0.64, 95% CI: 0.21-1.93), COVID-19-related intensive care unit admission (RR: 0.23, 95% CI: 0.04-1.39), COVID-19-related mortality (RR: 0.98, 95% CI: 0.35-2.74), all-cause hospitalization (RR: 0.99, 95% CI: 0.82-1.2), or all-cause mortality (RR: 1, 95% CI: 0.39-2.55) between the BCG vaccination and placebo groups. Conclusions: Current evidence from RCTs in older adults does not demonstrate a clinically meaningful protective effect of BCG vaccination against outcomes related to COVID-19; however, our certainty is limited by imprecision and variability in the context. More research is needed to examine the potential benefits of BCG vaccination in vulnerable groups, such as older adults.