BCG vaccine does not lower risk of COVID-19 infection among healthcare workers

1. In this randomized controlled trial, bacille Calmette-Guerin (BCG) vaccination did not result in a lower risk of contracting coronavirus disease 2019 (COVID-19) among healthcare workers as compared to placebo.

2. Vaccination with the BCG vaccine did not change the risk of symptomatic or severe COVID-19 among healthcare workers.

Evidence Rating Level: 1 (Excellent)

Study Rundown: The BCG vaccine was initially developed in order to prevent tuberculosis infection. Recently, it has been proposed to prevent respiratory illness generally in both children and adults. However, there is a knowledge gap in understanding whether the incidence and severity of COVID-19 among adult healthcare workers is lower in those who previously received the BCG vaccine compared to those who received a placebo. Overall, this study found that BCG vaccination did not reduce the risk of COVID-19 among healthcare workers compared to receiving a placebo. This study was limited by the inability to recruit the planned sample. Thus, the trial was underpowered and susceptible to type II error. Nevertheless, these study’s findings are significant, as they demonstrate that the BCG vaccine does not confer any protective benefit among healthcare workers in preventing symptomatic or severe COVID-19. This may help guide future COVID-19 prevention strategies.

Click to read the study in NEJM

In-Depth [randomized controlled trial]: This international, double-blind, placebo-controlled trial studied participants who were randomly assigned in a 1:1 ratio to receive either the intradermal BCG vaccine or saline placebo. Patients were followed for 12 months. Patients who had a previous positive SARS-CoV-2 test, contraindication to the BCG vaccine, receipt of BCG vaccine within the past year, any other live attenuated vaccine within the past month, or any COVID-19–specific vaccine were excluded from the study. The primary outcome measured was the incidence of symptomatic COVID-19 and the incidence of severe COVID-19 by six months follow-up. Outcomes in the primary analysis were assessed via survival analysis with adjustment for stratification factors based on a modified intention-to-treat protocol. Based on the primary analysis, the estimated risk of symptomatic COVID-19 by 6 months was 14.7% in the BCG group and 12.3% in the placebo group (risk difference, 2.4%; 95% confidence interval [CI], −0.7 to 5.5). When looking at the risk of severe COVID-19, the estimated risk of severe COVID-19 by six months was 7.6% in the BCG group and 6.5% in the placebo group (risk difference, 1.1%; 95% CI, −1.2 to 3.5). Additionally, the hazard ratio for any COVID-19 episode in the BCG group as compared with the placebo group was 1.23 (95% CI, 0.96 to 1.59). In summary, this study demonstrates that vaccination with the BCG vaccine did not result in a significantly lower risk of COVID-19 among adult healthcare workers.

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