Safety and COVID-19 Symptoms in Individuals Recently Vaccinated with BCG: a Retrospective Cohort Study

Summary Bacille Calmette-Guérin (BCG) induces long-term boosting of innate immunity, termed trained immunity, and decreases susceptibility to respiratory tract infections. BCG vaccination trials for reducing SARS-CoV-2 infection are underway, but concerns have been raised regarding the potential harm of strong innate immune responses. To investigate the safety of BCG vaccination, we retrospectively assessed coronavirus disease 2019 (COVID-19) and related symptoms in three cohorts of healthy volunteers who either received BCG in the last five years or not. BCG vaccination is not associated with increased incidence of symptoms during the COVID-19 outbreak in the Netherlands. Our data suggest that BCG vaccination might be associated with a decrease in the incidence of sickness during the COVID-19 pandemic (AOR 0.58, P < 0.05), and lower incidence of extreme fatigue. In conclusion, recent BCG vaccination is safe and large randomized trials are needed to reveal if BCG reduces the incidence and/or severity of SARS-CoV-2 infection.
Graphical Abstract
Highlights • Recent BCG vaccination is safe during the COVID-19 pandemic • BCG vaccination is not associated with symptoms of hyperinflammation • BCG might be associated with reduced incidence of sickness and extreme fatigue • Randomized trials of BCG vaccination for the prevention of COVID-19 are warranted
Moorlag et al. show in a retrospective cohort study that recent BCG vaccination is safe and did not increase disease symptoms during the COVID-19 outbreak. Prospective randomized clinical trials are warranted to assess BCG vaccination effectiveness against SARS-CoV-2 infection.