The Immunity Treadmill: How covid-19 vaccine resistance could perpetually push herd immunity out of reach

Collective resistance depends on how many unvaccinated people have already been infected, how many of them have immunity, and where they live.

I am sitting at a bar in Washington, DC waiting to get drinks and an early with an old friend. Everyone around me looks awkward. People are standing ever-so-slightly farther away than they did In The Before Time. Hand sanitizer comes in and out of purses like people are (still) avoiding the plague.

I’m sure I look off too; many of us haven’t been out to get dinner indoors in over a year. When my friend joins me, I’ll probably order a hamburger and a beer. Beer is one of the few things I haven’t made at home during lockdown. (My home brewing experiments did not go well).

Over time, I suspect we will all readjust to life in public. But how long will that take? At current rates, some scientists estimate it will take months before ~70% — one speculation of the herd immunity threshold for covid-19 — of people are vaccinated.

But the problem is not just one of projection; to estimate the likely share of the population with herd immunity, we also need to know (a) how many people will refuse to …