Professor Ajit Lalvani at Imperial College is involved in intriguing research on natural immunity to covid-19. He was on the Today programme on BBC Radio 4 (at about 8.37 am UK time). He has been investigating people who have been in close contact with infected people (for example, in the same household) but who don't develop the infection. He found that some of those people had memory T-cells effective against covid-19 that could have been generated by previous exposure to common cold coronaviruses (around a fifth of common colds are caused by coronaviruses). The picture is not at all black and white, but there is the basis for further promising research that could, conceivably, lead to a new generation of vaccines that would be variant-proof. Watch that space.

You can google his name and include the word "covid" to get several references.