Trevor Bedford took a crack at estimating the steady state back in October (so pre-Omicron). He came up with estimates of 20-30% of the population infected annually and deaths of 40K-100K per year in the US. https://twitter.com/trvrb/status/1448297978419101696 . Unfortunately, he didn’t show enough of his work for me to understand where the 20-30% number comes from. Deaths is just multiplying number of infections by IFR. The big question mark here is whether high risk people will continue to get boosters; Bedford is guessing yes.
Here is my own attempt to estimate number of infections. I googled “how long does covid acquired immunity last” and looked for useful studies. My impression is that no one really knows, but experts generally give numbers in a range of 6 months − 5 years, and tend to center their guesses on 2-3 years. (Since this is presumably an exponential decay process, it isn’t crazy to think that we could have estimates on the half life of immunity, even though the disease has only been around 2 years.) A very naive guess would then be to expect people to get infected every 2-3 years, so 30-50% of the population each year.
But life is better than this! The infectious period is about 5 days, so if the natural immunity period is 2 years then one can’t expect more than (5 days)/(2 years) = 0.6% of the population to be infected at a time. In a population with only 0.6% infected, one could live a 2019 lifestyle for months or probably years—without getting infected. And this forms a virtuous cycle where the small number of infected people means one can go on longer without being infected. I didn’t attempt to solve for equilibrium in the mathematical sense, but 3-5 years between infections doesn’t seem crazy.
If people kept getting boosters, the numbers would be much better. And we could start timing them to the seasonality of the disease, just like with the flu. To me personally, it is clear that the cost-benefit of getting a COVID booster every Fall for the rest of my life is worth it. But most people I talk to, even in my liberal bubble, think that is crazy, so I’m going to assume this is not a significant effect.
I’d love to see more intelligent attempts to solve for the steady state.
As a minor addendum, I asked microcovid what it thought about spending 4 hours a day indoors unmasked with 20 people, but with a community incidence of 0.5%, attempting to simulate 2019 living with broad acquired immunity. It thinks this is 19,000 microcovids, suggesting it would still lead to infection in 50 days. This is depressing, I had hoped for a lot more gain than that.
Trevor Bedford took a crack at estimating the steady state back in October (so pre-Omicron). He came up with estimates of 20-30% of the population infected annually and deaths of 40K-100K per year in the US. https://twitter.com/trvrb/status/1448297978419101696 . Unfortunately, he didn’t show enough of his work for me to understand where the 20-30% number comes from. Deaths is just multiplying number of infections by IFR. The big question mark here is whether high risk people will continue to get boosters; Bedford is guessing yes.
Here is my own attempt to estimate number of infections. I googled “how long does covid acquired immunity last” and looked for useful studies. My impression is that no one really knows, but experts generally give numbers in a range of 6 months − 5 years, and tend to center their guesses on 2-3 years. (Since this is presumably an exponential decay process, it isn’t crazy to think that we could have estimates on the half life of immunity, even though the disease has only been around 2 years.) A very naive guess would then be to expect people to get infected every 2-3 years, so 30-50% of the population each year.
But life is better than this! The infectious period is about 5 days, so if the natural immunity period is 2 years then one can’t expect more than (5 days)/(2 years) = 0.6% of the population to be infected at a time. In a population with only 0.6% infected, one could live a 2019 lifestyle for months or probably years—without getting infected. And this forms a virtuous cycle where the small number of infected people means one can go on longer without being infected. I didn’t attempt to solve for equilibrium in the mathematical sense, but 3-5 years between infections doesn’t seem crazy.
If people kept getting boosters, the numbers would be much better. And we could start timing them to the seasonality of the disease, just like with the flu. To me personally, it is clear that the cost-benefit of getting a COVID booster every Fall for the rest of my life is worth it. But most people I talk to, even in my liberal bubble, think that is crazy, so I’m going to assume this is not a significant effect.
I’d love to see more intelligent attempts to solve for the steady state.
As a minor addendum, I asked microcovid what it thought about spending 4 hours a day indoors unmasked with 20 people, but with a community incidence of 0.5%, attempting to simulate 2019 living with broad acquired immunity. It thinks this is 19,000 microcovids, suggesting it would still lead to infection in 50 days. This is depressing, I had hoped for a lot more gain than that.