I'm deeply confused by the so-called herd immunity (aka herd mentality) strategy. I don't just mean that I think this is a bad idea, but I think this strategy is fundamentally nonsense.

When we talk about herd immunity, we're talking about vaccinating enough of a population s.t. when (a limited number) introductions of a disease occur, transmission is not sustained.

If we reach the 60-70% immune with SARS-CoV2 required for herd immunity with infection, infections will not magically stop happening.

Due to birth/death/children starting school, there will always be a steady supply of new susceptibles. At the same time, when we reach 60-70% immune, we will still have a massive number of cases. R will be close to 1.

These are not conditions for elimination. These are conditions to establish an *endemic equilibrium.* Cases will on average exactly replace themselves and more and more of the population will get infected.

So, let's be precise. Herd immunity via infection is not a strategy. What we're really talking about is SARS-CoV2 becoming an endemic disease. To talk about herd immunity as a strategy we need a vaccine, or some other control measure. *Everyone getting infected is not control.*

#epitwitter