Welcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: Long Covid Risks: 2023 Update, published by Elizabeth on May 6, 2023 on LessWrong.

Back in 2021 I wrote a post estimating the risk of long covid. Recently a client hired me to do an update, focusing on changes induced by Paxlovid and vaccination. This was a <5h project and the literature wasn’t very rich so nothing I say here is conclusive, but nothing I said last time was conclusive either so let’s enjoy this together.

Some caveats:

I spent 5 hours on this, and that includes client-specific work I’m not including here.

Research that met my standard was really scarce; ultimately each conclusion is based on a single study. My goal was data that includes a large population not selected for having long covid, where reporting was automated so you don’t need to worry about response bias. In practice, this means I used data from large medical systems with integrated reporting, like the American Department of Veteran Affairs, national medical systems, and HMOs. Surveys from long covid support groups were ignored with prejudice.

Summary

Vaccination helps, a bit: Given a medically diagnosed infection (which means it was serious enough to actually get you to the doctor), up-to-date vaccination lowers the risk of long covid by about 20% (this does not include the reduction in risk of having diagnosable covid in the first place, which is substantial).

Paxlovid helps, more: Nirmatrelvir, which is one of two drugs that make up Paxlovid, reduces long covid risk by about 30% for medically diagnosed infections (which means it was serious enough to actually get you to the doctor). An optimist might hope the other drug (which is in the same class, although most commonly used as an adjuvant) is also useful and round this to 50%.

Most symptoms are temporary: Long covid does tend to get better over time, but how quickly depends on the symptom. At one year post-infection, the rate of heart issues is nearly indistinguishable from controls, but cognitive issues have a 50% chance of persisting.

Calculate your absolute risk: Your absolute risk depends on your age and comorbidities. The measured risk for 70-year-old men (not controlling for comorbidities) of developing at least one serious sequelae of medically diagnosed covid n (which means it was serious enough to actually get the patient the doctor) is ~12%. If you want to norm this for your own demographic, you can get a very crude estimate by entering your demographic information in this calculator, dividing your risk of hospitalization by 3 and multiplying the total by 0.4 (which includes the 20% reduction from vaccination and the 50% reduction from Paxlovid). If you are a cis woman, multiply by 2 to account for increased risk (trans people: I have no idea, if you find good data please let me know).

I cannot emphasize enough how crude this is. I got that 3 by making up a 70 year old man with some common comorbidities, which has a risk of hospitalization of ~36%, and noticed 36/12=3. I don’t think The Economist has been keeping up to date with the latest strains of covid or even the impact of vaccination; these proposed calculations are strictly for order-of-magnitude estimates.

Sample calculation: a 35 year old woman with no comorbidities shows a 3.8% risk of hospitalization (with their data, which I believe is very old). 3.8%/3= 1.3%. 1.3%0.4= 0.5%. Times 2 for being female = 1.0%. So a covid infection bad enough to require medical attention has a 1 chance in 100 of a serious persistent issue post-covid.

Studies

Nirmatrelvir and the Risk of Post-Acute Sequelae of COVID-19 (pre-print)

This study compared people who got covid and received Nirmatrelvir (half of Paxlovid). It used data from the American Department of Veteran Affairs, which means the participants are older (average age 65), overwhelmingly male (~90%), and very white (75%). La...