Thread by @profshanecrotty

1/ Our new perspective piece on “Crossreactive memory T cells and herd immunity to SARS-CoV-2”is out now.
@mlipsitch @yonatan @SetteLab @ljiresearch @NatRevImmunol

nature.com/articles/s4157…

2/ Given the amount of discussion in scientific, public, and political spheres, it is useful to undertake a thought experiment examining crossreactive T cell effects on COVID-19 disease severity and herd immunity, should crossreactive memory T cells confer some form of protection

3/ We consider immunological and epidemiological aspects and implications of pre-existing crossreactive immune memory to SARS-CoV-2, largely originating from previous exposure to circulating common cold coronaviruses.

4/ We propose four immunological scenarios for the impact of crossreactive CD4+ memory T cells on COVID-19 severity and viral transmission. For each scenario, we discuss implications for herd immunity and projections of the global impact of SARS2.

5/ In sum, we argue potential impacts of crossreactive T cell memory are already ‘baked in’ to epidemiological models, particularly regarding herd immunity.

6/ The implications of immunological processes on other aspects of SARS2 epidemiology are worthy of future study, and discussed in the paper.

7/ We emphasize that any functional role for crossreactive T cell memory in COVID-19 remains unproven, but the thought experiment is helpful.

nature.com/articles/s4157…