Thread by @AstorAaron

If you're trying to calculate national herd immunity at this point, I think we are at ~76%. 52% with a first vax dose + 32% previously infected (based on Youyang Gu's Feb estimate). Assume ~52% of infected were also vaccinated, that's 52+17=69%. But then add 7 for under 12s->76%.

Assumptions and caveats:
1) Under 12s very rarely transmit, which is why I'm backing them out of the analysis.
2) Same ratio of vaxxed among previously infected and not infected
3) Counting just "first dose" jumps the gun a bit, but one dose still confers lots of protection.

4) Stronger variants like Delta/B.1.617.2 will probably change the "one dose" figure. But that 42% fully vaxxed number should reach the partial vax number in a few weeks, and 2 doses work well on Delta.
5) Major regional disparities

6) Seasonality gives a reprieve for now. We'll now by end of June how the less-vaxxed South does compared to last summer's spike.

7) We'll also know by late summer if Delta reinfects. My guess is that it doesn't in most cases.
8) Nobody really knows what herd immunity threshold is needed to turn covid from pandemic to minor endemic. Could be 80% or 90%. Either way, I don't think we are far off.

I think CDC was right to relax distancing & mask guidelines in May. I also think remaining mask/distancing requirements for under 12s should be lifted. Best way to protect kids is if their parents get vaccinated. But they are still mercifully at low risk of infection or illness.

As a general matter, NPIs have reached the end of their usefulness. (I won't get into the debate here over exactly how effective they were). But there is still real risk out there for unvaccinated-and-not-previously-infected adults, esp. if they have comorbidities.

I'd be especially concerned about unvaxxed obese, hypertension, diabetic, and/or asthmatic people ages 14-45. There are a LOT of people in this category and they need to get vaccinated ASAP.