Just getting around to reading this paper on, inter alia, t-cell response in seronegative persons. H/T @andreasantlab. Key quote:

Robust T cell immunity in convalescent individuals with asymptomatic or mild COVID-19 https://www.biorxiv.org/content/10.1101/2020.06.29.174888v1

Twice as many healthy blood donors showed t-cell response as showed seropositivity (antibodies).

So seroprevalence studies w/o t-cell assays may substantially underestimate population-level immunity to COVID.

@ATabarrok @sarahcobey @maciekboni

This paper notes that t-cells persist for many years after infection with SARS-CoV-1. Moreover, see this quote.

So, if you do multiple rounds of cross-sectional population surveys, t-cell assays are better able to measure growth in population level immunity. Antibodies decline over time, which generates negative bias in estimates of that immunity.

@anuacharya @NeelanjanSircar @sidrup

The real challenge is getting t-cell assays into surveys of population-level immunity to COVID. They are costly and harder to implement. But they are an important step to determining target levels for vaccination policy.

@profmohanan @anup_malani @nebuer42 @tylercowen