BACKGROUND Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused more than 1 million deaths worldwide; thus, there is an urgent need to develop preventive and therapeutic strategies. The antituberculosis vaccine bacillus Calmette-Guérin (BCG) demonstrates nonspecific, protective innate immune–boosting effects. Here, we determined whether a history of BCG vaccination was associated with decreased SARS-CoV-2 infection and seroconversion in a longitudinal, retrospective observational study of a diverse cohort of health care workers (HCWs).METHODS We assessed SARS-CoV-2 seroprevalence and collected medical questionnaires, which included information on BCG vaccination status and preexisting demographic and clinical characteristics, from an observational cohort of HCWs in a multisite Los Angeles health care organization. We used multivariate analysis to determine whether a history of BCG vaccination was associated with decreased rates of SARS-CoV-2 infection and seroconversion.RESULTS Of the 6201 HCWs, 29.6% reported a history of BCG vaccination, whereas 68.9% had not received BCG vaccination. Seroprevalence of anti–SARS-CoV-2 IgG as well as the incidence of self-reported clinical symptoms associated with coronavirus disease 2019 (COVID-19) were markedly decreased among HCWs with a history of BCG vaccination compared with those without BCG vaccination. After adjusting for age and sex, we found that a history of BCG vaccination, but not meningococcal, pneumococcal, or influenza vaccination, was associated with decreased SARS-CoV-2 IgG seroconversion.CONCLUSIONS A history of BCG vaccination was associated with a decrease in the seroprevalence of anti–SARS-CoV-2 IgG and a lower number of participants who self-reported experiencing COVID-19–related clinical symptoms in this cohort of HCWs. Therefore, large randomized, prospective clinical trials of BCG vaccination are urgently needed to confirm whether BCG vaccination can confer a protective effect against SARS-CoV-2 infection.
Magali Noval Rivas, Joseph E. Ebinger, Min Wu, Nancy Sun, Jonathan Braun, Kimia Sobhani, Jennifer E. Van Eyk, Susan Cheng, Moshe Arditi
Demographics and clinical characteristics of the HCWs cohort used in this study based on influenza vaccination status