The COVID-19 has started from China and spread to all countries within a very short period. The severity of the disease varies from one patient to another as well as one country to another. It depends on the immune status of individuals simultaneously on the quality of the environment and customs of a particular country. Various factors are studied in correlation with the severity of disease like specific dietary supplements, previous exposure to related antigens, age, and health of individual and previous vaccinations, and many more. Different vaccines play an essential role to reduce the severity of various infectious diseases like TB, Measles, etc. Few bacterial vaccines also showed non-specific activity against viral infections like the BCG vaccine. The efficacy of BCG vaccine against several viral infections reported in several countries like West Africa, South Africa, Australia, etc. BCG was found to be associated with the reduction in children’s mortality rate due to respiratory infections in Haiti, Southeast Asia, United Kingdom, etc. This study focused on BCG vaccination concerning the severity of disease among the vaccinated and non-vaccinated population. Further, the study explained the role of BCG in viral inactivation with emphasis on the COVID-19 virus. We found low severity of SARSCoV- 2 infections in universal BCG implemented countries as compare to the non-universal implemented countries. The current study explored that the BCG vaccine is showing a strong correlation in the reduction of the severity of COVID-19 infection.
BCG, COVID-19, Non-specific, Immune response, Trained-immunity, Cytokines