https://www.cell.com/action/showPdf?pii=S0092-8674(20)30610-3

Very interesting article. Still in process for final printing, but has already been peer reviewed and accepted. Some types of common cold (which are caused by similar coronaviruses) may possibly (not quite 100% sure yet) provide immunity against COVID-19. Reminds me that Louis Pasteur defeated smallpox by vaccinating people with cowpox, which was much, much less virulent. Could a vaccination against COVID-19 be this simple?

NOTE: Don't forget that, according to HG Wells, the common cold killed the Martians too. LOL.