Thread by @phylogenomics

Based on this Tweet I decided to look for myself at the new guidance from the @CDCgov for vaccinated people 1/n

https://twitter.com/PanickedFoodie/status/1420138346983084033

If you go to the CDC page on #COVID19 you see "Guidance for people fully vaccinated" cdc.gov/coronavirus/20… 2/n

Click on the "Learn More Button" and you see this: 3/n

The part of this that is perhaps most vexing, and I think generally not wise is this part "To maximize protection from the Delta variant and prevent possibly spreading it to others, wear a mask indoors in public if you are in an area of substantial or high transmission." 4/n

This links to the following website covid.cdc.gov/covid-data-tra… showing a county by county view of putative community transmission levels 5/n

In theory one is supposed to check the county levels for one's area and use that to determine whether indoor masking is needed to the vaccinated 6/n

This seems pretty unsound. Yes, county community transmission can be a component of determining risk but others factors almost certainly more important incl where one is going indoors, # of people there, ventilation & air filtering, time, activity levels and more 7/n

Plus, heterogeneity within a county is almost certainly very high with some parts of a county differing enormously from others - I simply do not get at all the focus on county community transmission levels over other factors 8/n

And don't even get me started on the next part - completely weak / lame "If this applies to you or your household, you MIGHT choose to wear a mask". No recommendation at all from @CDCgov to protect people at higher risk 9/n

And while we are at it, the focus on county levels, rather than on other aspects of risk (eg, density, ventilation, air filtering) is disappointing (though it is briefly mentioned here cdc.gov/coronavirus/20… re: immunocompromised people) 10/n