[blueplum]

because in this study they were comparing the three vaccines.

yes, you have natural killer cells but unless they are exposed to covid, they aren’t ‘tuned’, so your ‘unvaccinated’ candidate would have to be an infected recovered to compare apples to apples.

[teeman8r]

but how many of the vaccinated actually had covid and the natural immunity too?

[WildHighlander57]

So, why don’t they test a group of covid-recovered people and compare T-cell levels?

They might not get the results they wanted; recovered folks might have higher levels.