I think articles like this do not sit well with the strong pro covid-19-vaccine, facemask and lockdown leaning crowd on HN. This is another interesting article about long lasting immunity against covid-19. Which I believe is a good counter against the often told herd immunity requires x percent antibodies in the population argument:
https://www.nature.com/articles/d41586-020-02400-7https://agencia.fapesp.br/herd-immunity-to-novel-coronavirus...