Should Bacillus Calmette–Guérin (BCG) vaccine be used in the prophylaxis of COVID-19?

Abstract

At present, there is insufficient evidence to support the use of BCG vaccine as prophylaxis for COVID-19. Bacillus Calmette Guerin (BCG) vaccine is an attenuated microorganism derived from bovine tubercle bacillus and is being given to prevent severe tuberculosis. BCG vaccination may enhance production of antibodies and pro-inflammatory cytokines such as interleukin (IL)-1β and tumor necrosis factor (TNF). BCG may lead to increased CD4 and CD8 T-cell activity on subsequent viral infection. Ecological studies on the effect of BCG vaccination policy on COVID-19 outcomes have conflicting results and are prone to bias from confounders. There is insufficient evidence on the efficacy and safety of BCG vaccine for COVID-19 prophylaxis. Thirteen clinical trials are ongoing among high-risk groups (healthcare workers, elderly, police officers) to evaluate the efficacy and safety of BCG vaccine in preventing COVID-19 and its severe symptoms. WHO does not recommend the use of BCG vaccine as prophylaxis against COVID-19. Adverse events of BCG vaccine range from mild local cutaneous reactions to systemic adverse events such as abscess, lymphadenopathy and osteomyelitis.