The effect of BCG vaccination on infection and antibody levels against SARS-CoV-2-The results of ProBCG: a multicenter randomized clinical trial in Brazil

Objectives: Evatuate if Bacillus Calmette-Guerin (BCG) vaccine could be used as a tool against SARS-CoV-2 based on the concept of trained immunity.Methods: A multicenter, double-blinded, randomized clinical trial recruited health care workers (HCWs) in Brazil. The incidence rates of COVID-19, clinical manifestations, absenteeism, and adverse events among HCWs receiving BCG vaccine (Moreau or Moscow strains) or placebo were compared. BCG vaccine -mediated immune response before and after implementing specific vaccines for COVID-19 (CoronaVac or COVISHIELD) was analyzed. Cox proportional hazard and linear mixed effect modeling were used.Results: A total of 264 volunteers were included for analysis (BCG = 134 and placebo = 130). The placebo group presented a COVID-19 cumulative incidence of 0.75% vs 0.52% of BCG. The Moreau strain also pre-sented a higher incidence rate (1.60% x 0.22%). BCG did not show a protective hazard ratio against COVID-19. In addition, the log (immunoglobulin G) level against SARS-CoV-2 presented a higher increase in the BCG group, whether or not participants had COVID-19, but also without statistical significance.Conclusion: Our results suggest that BCG has a tendency of protection against SARS-CoV-2 and higher immunoglobulin G levels than placebo. The clinical trial was registered at https://clinicaltrials.gov/ (NCT04659941).(c) 2023 The Authors. Published by Elsevier Ltd on behalf of International Society for Infectious Diseases. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

Automated summary

This study evaluated the effectiveness of Bacillus Calmette-Guerin (BCG) vaccine as a tool against SARS-CoV-2 based on the concept of trained immunity. A multicenter, double-blinded, randomized clinical trial recruited health care workers (HCWs) in Brazil. The incidence rates of COVID-19, clinical manifestations, absenteeism, and adverse events among HCWs receiving BCG vaccine (Moreau or Moscow strains) or placebo were compared. BCG vaccine-mediated immune response before and after implementing specific vaccines for COVID-19 (CoronaVac or COVISHIELD) was analyzed using Cox proportional hazard and linear mixed effect modeling.