Thread by @GovindPersad

This is the most compelling slide in the set, and makes a very good case for universal masking right now, which I agree with.

However, I'd have liked to see CDC grapple with this: what's the overall reduction in R if vaccinated people mask, but unvaccinated people don't?

1/5

https://twitter.com/JuliaRaifman/status/1420916456540225539

My other concern about some framing (in reporting/Twitter, not the slides) is that it may fuel the following misinterpretation: "a vaccinated/vaccinated person encounter is as likely to transmit Covid as an unvaccinated/unvaccinated one"

That isn't what the slides/data say!
2/5

Even if we assume breakthroughs are just as likely to produce an infectious dose as an unvaccinated person's infection (stronger than CDC's claim):

- vaccines make people much less likely to *be* infectious
- vaccines reduce susceptibility to an otherwise infectious dose

3/5

This thread gives a nice explanation:

https://twitter.com/nataliexdean/status/1418577845958320128?s=20

Assume 50% vaccine coverage that is 80% effective vs infection but 0% effective vs. transmission once infected (very pessimistic assumption)

Still just (.5*.2)/((.5*.2)+.5))=16.6% of transmission from vaccinated

4/5

So while I agree indoor masking by vaccinated people has benefits, dunking on the "pandemic of the unvaccinated" claim is too quick.

Nothing in the CDC deck contradicts the following:

Unvaccinated/unvaccinated encounters are *much* likelier to spread Covid than vaxed/vaxed ones