Is the BCG Vaccination Effective against COVID-19?

Aims and objectives: Vaccine is one of the most effective tools available to prevent infectious diseases and their complications. One of the most controversial vaccines for its therapeutic effect on COVID-19 is the BCG vaccine. The BCG vaccine has been used worldwide since 1921. The first BCG strain was introduced in 1947, but mass production and nationwide prescribing began in 1984. The BCG vaccine is able to stimulate the immune system's response to a large number of antigens that are effective in causing infectious diseases. Involved mechanisms include activation of NK and NKT memory cells and an increase in 1β-IL against viral infections. Results: Due to the prevalence of COVID-19 virus and the need for research to become more aware of the virus and the process of prevention, control and treatment, there is hope of the effectiveness of the BCG vaccine in recovering diseases. Studies show that tuberculosis infection, both active and latent, increases the severity and progression of the disease in people with COVID-19. The BCG vaccine is likely to be able to reduce the cytokine storm after exposure to SARS-COV-2, resulting in mild COVID-19 and early recovery. Children also seem to be protected against COVID-19 compared to adults. In late adulthood, mechanisms such as the reduction of regulatory T cells can help exacerbate COVID-19. Conclusions: Despite all the studies, the claim that the BCG vaccine is effective against COVID-19 needs further investigation worldwide. Any incorrect information and lack of accurate tests can lead to misuse of the vaccine and this can lead to the deprivation of children in need of vaccine in some countries due to its lack. As a result, it is better to conduct more comprehensive studies to obtain definitive results.