Thread by @profshanecrotty

What about vaccinating people who have already had COVID? I get this question a lot. New answers now! 🧵
nytimes.com/2021/02/01/hea…

Excellent and rapid work to find that, for people who have previously had COVID, one COVID vaccine dose gives a bigger antibody response than seen in COVID-negative people receiving a normal two dose COVID vaccine regimen.

One study by Viviana Simon & @florian_krammer and colleagues. And an independent stduy by Sajadi and colleagues in Maryland.

One dose of vaccine gave high binding antibody titers
medrxiv.org/content/10.110…

And in the Sajadi study found high neutralizing antibodies.
medrxiv.org/content/10.110…
While they don't have the direct comparison group of COVID-negative people who received two vaccine doses, those neutralizing titers are convincingly high, and they track with the binding antibody

I have no problem with health officials who want to keep the vaccine schedule based on the Phase 3 trial data. But, to me, these data are convincing enough, in the context of current vaccines EUAs, that people with previously confirmed COVID-19, a single dose of vaccine is enough

, and with fewer side effects.

To be clear, in a non-pandemic situation, the data one would want to make such a recommendation would be quantitation of the following, in comparison to the regular COVID RNA vaccines schedule:

- side effects
- Neutralizing antibody titers
- T cell responses
- Durability of both antibodies and T cells

But, for me, the combo of high neutralizing/binding antibodies and the side effect reports are enough, even if it is a temporary recommendation for current pandemic conditions.

The question of WHEN a person with previously confirmed COVID should be immunized is a different question.

As previously mentioned, waiting 90 days is reasonable.

https://twitter.com/profshanecrotty/status/1350478079081123841?s=20

and the NEJM allows for a similar conclusion

https://twitter.com/profshanecrotty/status/1350478079915769858?s=20

Additional data could support different schedules in the future. But, while there is certainly evidence of immune memory and protective immunity against COVID lasting 6+ months (see our other work and tweets),

as I said on the BBC show The Evidence this past week, nothing compares to a Phase 3 clinical trial for proof! That is to say, the vaccines definitely protect, so the wisest course of action is to get vaccinated when you can.