"Covid-resistant people inspire new vaccine tactic"
Seems some people were already infected with a corona virus of a non-covid variant, leading to a cross immunity and a prepared immunosystem
https://www.bbc.com/news/health-59207466
This might explain why the 'first wave' vaccine shots can also help against new corona variants and their successors.
Seems all corona-virus infected cells are being recognized by the human immunosystem T-cells (infected cell surfaces look different for the i.-system), so regardless what is inside the hijacked cells are being destroyed before the virus can multiply.