A long-standing hypothesis suggests the BCG vaccine also serves to generally enhance the immune system, meaning it could protect against covid-19, and trials are underway to find out
Source:
https://www.newscientist.com/article/2241590-bcg-vaccine-being-trialled-as-potential-protection-against-covid-19/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home