Updates

12/29/21: I am not making anything remotely resembling an attempt to document a comprehensive update of this for Omicron, but capturing a few further updates here, mostly for my own reference; maybe you will find them helpful too. If you have further thoughts please chime in!

Relevant snippets from Zvi's 12/28/21 post, "Omicron: My Current Model":

• Summary: "Long Covid risk small but real for all age groups, vaccination likely helps a lot."
• Details: "Long Covid is real but rare and risk scales with severity. This is not something we can be confident in, and there are big unknowns to be sure, but my baseline continues to be that Long Covid risks are mostly proportional to short-term serious Covid risks aside from not scaling as much with age, and other things that reduce one reduce the other. Long Covid is still the biggest downside to getting Covid if one is young. I wish I could put a magnitude on this risk, but my best guess continues to be that this is not that much worse or different than e.g. Long Flu or Long Lyme, sometimes getting diseases does longer term damage than we realize and curing and preventing disease is therefore even more valuable than we think. But to extent you worry, Paxlovid probably does a lot to prevent this, so holding out until it is available would help you here."

Reasons to think the situation may be worse than Zvi's assessment above  (I don't know if Zvi has incorporated these findings into his model or missed them... posted a comment here to see if he can chime in on that):

• 9/29/21 NPR article recapping a study from around that time
  • Affects over 1/3 of COVID sufferers, 2x as high as for flu:
    • "In the study published Tuesday in the journal PLOS Medicine, researchers found that about 36% of those studied still reported COVID-like symptoms three and six months after diagnosis. Most previous studies have estimated lingering post-COVID symptoms in 10% to 30% of patients.
    • ...Although long COVID is poorly defined, the researchers looked at such symptoms as chest/throat pain, abnormal breathing, abdominal symptoms, fatigue, depression, headaches, cognitive dysfunction and muscle pain.
    • ... the new study concludes that the chances of getting COVID-19 symptoms months after the acute stage of the illness was more than twice as high as for influenza."
  • Other points to consider:
    • "The Oxford-led team also found that people who had more severe COVID-19 illness were more likely to get long COVID. Likewise, female and young adult patients also had an elevated risk for the long-term symptoms, but the authors of the study found no difference between white and nonwhite patients."
• 11/24/21 Reuters article noting that "COVID-19 vaccines are highly effective in protecting against serious illness, but they do not protect against "long COVID" in people who become infected despite vaccination"
  • (However, both the article and the study it cites note that vaccines are protective against long COVID to the extent that they prevent infection in the first place.)

ORIGINAL POST (written early Sept 2021)

As I plan a short upcoming trip, I've been thinking through how much COVID risk I'm willing to take. (Prior to this, as a fully vaccinated, reasonably healthy person, I've been roughly managing to a weekly budget of 200 microCOVIDs in the Delta era, based on microCOVID.org's assertion that this is roughly comparable to the risk of long-term consequences from driving regularly, which seems to roughly capture my level of risk aversion.)

In doing so, I went through the recent posts by Zvi, Scott Alexander, and Elizabeth that speak to this question, as well as the comments on Scott's post. I figured it may be helpful to share my summary conclusions and snippets, even though they are not super well synthesized (I'm kind of out of cycles for the day in thinking about this).

To be clear, I have not put much independent thought into analyzing the assertions I've quoted below, as I trust the people who've written those posts to be much better at this analysis than I am. 

I'd be curious if anyone has thoughts or findings that materially change the conclusions I've reached or summarized here.

Also, if anyone quoted objects to my briefing their posts as I've done here (or generally folks think that this post is more noisy than helpful), please let me know!

My personal conclusions

• I'll be bumping my budget up to at least 400 microCOVIDs/week, given that vaccination seems to cut risk by at least half. (Basing that on this microCOVID blog post earlier, and the fact that the posts below conclude that the risk is lower than that).
• It's probably worth bumping my budget even higher, given Zvi, Scott, and Elizabeth's conclusions. Not sure how I evaluate that. Any suggestions would be welcome.
• It's worth looking at hospital capacity as well in making travel plans - that matters regardless of personal COVID risk

Summary assessments

• "basically, ‘don’t do stupid stuff’ still applies, but I have no intention of going beyond that rule, or forming a microCovid budget or anything similar to it." - but hasn't read the Matt Bell post yet (Zvi 9/2)
  • "I haven’t yet done a full reading of the Matt Bell post that Scott references. It is long and I do not currently have the time. I hope to read it carefully over the coming week.I didn’t update much in aggregate, at least for practical purposes. Long Covid seems legitimate, and worth a nonzero amount of effort to minimize, but my model says it is mixing a lot of things together, is largely typical of what happens after being sick, is protected against by vaccines similarly to how they protect against symptomatic disease, and in many studies they go on a fishing expedition for symptoms then attribute everything that happens chronologically after Covid to Covid. Thus, basically, ‘don’t do stupid stuff’ still applies, but I have no intention of going beyond that rule, or forming a microCovid budget or anything similar to it."
  • Key takeaways from Matt's (8/11/21) post:
    • "The US will almost certainly have a big spike of Delta cases in mid August to September.  Try to not get sick when everyone else is getting sick, as it will be harder to get good medical attention, and if you are in a less-vaccinated area, the hospitals may be full of mostly unvaccinated people sick with Delta.
    • Delta is much more transmissible than original COVID, and somewhat deadlier (at least, for the unvaccinated).
    • If you’re young, healthy, vaccinated, and catch Delta, you’ll likely have a relatively mild acute infection, and your chance of hospitalization or death will be very low.  However, you’ll run a significant chance (possibly a ~2.5% chance, but this is a low-confidence estimate) of acquiring some long-term chronic condition (eg brain fog, decreased lung function, chronic fatigue, loss of smell or taste) that doesn’t go away for many years, perhaps for the rest of your life.  These long term chronic conditions vary in their severity – of the people who got long COVID after a mild COVID infection, about 18% said that their long COVID limited their daily activities a lot.  You’ll have to make your own decision on how hard you want to work to avoid this risk.
    • Your protection from catching a Delta infection, and your risk of getting long COVID, depends substantially on how recently you were vaccinated, with some evidence of a gradual dropoff in protection more than 4 months after your second shot.  This is why many governments are starting to look at 6-month booster shots.  If you had a single-dose J&J shot, you'll want to get a single-shot mRNA booster now.  It's backed up by safety and efficacy research, and many vaccination sites are now willing to do this.
    • A vaccinated person who works to keep their risk of infection from Delta low has a ~1/6x  chance of catching long COVID relative to an equivalently behaving unvaccinated person (again, this is a low-confidence estimate based on limited data).
    • If you want to have a low chance of catching Delta, you’ll need to go back to minimizing indoor unmasked contact outside your household, including with vaccinated people, and wearing a good mask (N95 or better) in stores and other public settings.  As before, if you do choose to socialize indoors, 1-on-1 hangouts are much safer than indoor parties or big dinners.
    • Your choices can slow the spread of Delta in your social network and beyond.  If you feel sick at all or find out you were exposed, avoid socializing for a few days.  If you are sick, take a COVID test immediately.  If you find out you were exposed, get tested 3-5 days after exposure.  Keep avoiding socializing until symptoms disappear and you get a negative test result.  Don’t be that person who gives your friend a lifelong chronic medical condition.
    • There will probably be much better information in the next few weeks on the incidence of long COVID among vaccinated people who catch Delta.  You may want to consider being extra cautious until we learn more.
    • It’s hard to predict what things will look like a few months out.  Other more immune-escaping variants might come out at any time and further change the landscape.  Booster shots targeted at Delta and future variants are also coming in a few months."
• "The threat of Long Covid while not zero is not so large as to distinguish it from numerous similar background risks we take all the time with such matters." (Zvi 9/2, citing Elizabeth)
  • Elizabeth's fuller guidance:
    • "My tentative conclusion is that the risks to me of cognitive, mood, or fatigue side effects lasting >12 weeks from long covid are small relative to risks I was already taking, including the risk of similar long term issues from other common infectious diseases. Being hospitalized would create a risk of noticeable side effects, but is very unlikely post-vaccine (although immunity persistence is a major unresolved concern).
    • I want to emphasize again that “small relative to risks you were already taking” doesn’t necessarily mean “too small to worry about”. For comparison, Josh Jacobson did a quick survey of the risks of driving and came to roughly the same conclusion: the risks are very small compared to the overall riskiness of life for people in their 30s. Josh isn’t stupid, so he obviously doesn’t mean “car accidents don’t happen” or “car accidents aren’t dangerous when they happen”. What he means is that if you’re 35 with 15 years driving experience and not currently impaired, the marginal returns to improvements are minor.
    • And yet. I have a close friend who somehow got in three or four moderate car accidents in < 7 years, giving her maybe-permanent soft tissue damage (to answer the obvious question: no, the accidents weren’t her fault. Sometimes she wasn’t even driving). Statistically, that friend doesn’t exist. No one gets in that many car accidents that quickly without it being their fault. And yet the law of large numbers has to catch up with someone. Too small to measure can be very large.
    • What this means is not that covid is safe, but that you should think about covid in the context of your overall risk portfolio. Depending on who you are that could include other contagious diseases, driving, drugs-n-alcohol, skydiving, camping, poor diet, insufficient exercise, too much exercise, and breathing outside. If you decide your current risk level is too high, or are suddenly realizing you were too risk-tolerant in the past, reducing covid risk in particular might not be the best bang for your buck. Paying for a personal trainer, higher quality food, or a HEPA filter should be on your radar as much as reducing social contact, although for all I know that will end up being the best choice for you personally."
  • Things that would change her conclusion:
    • "My own behavior and plans have changed a lot based on this research, so I’m extremely interested in counterarguments. To make that easy, here’s a non-exhaustive list of things that would change my mind:
      • Evidence that long covid gets worse over time, rather than slowly improving (note that I did look at data from SARS 1 and failed to find this).
      • New variants increase the risk to what it was or was feared to be in April 2020
      • Evidence of more severe vaccine attenuation than we’re currently seeing.
      • Credible paths through which the risk could drop shortly in the next six months."
• "Your risk of a terrible long COVID outcome conditional on COVID is probably between a few tenths of a percent and a few percent." (Zvi 9/2, citing Scott)
  • "This is the headline number that matters, noting that this is conditional on symptomatic Covid rather than Covid, and terrible is being conflated with serious. He notes the disagreement with the first post I linked to, and tries to then do a Fermi calculation of the chance of getting Long Covid if one lived a normal life, and gets very wide bounds, somewhere between 1 in 150 and 1 in 25,000. I think we can safely throw out the upper part of his range, as I think a 10% chance of breakthrough symptomatic Covid within a year isn’t reasonable if you do a little math, and it’s starting at 25% which seems higher than the studies referenced above would suggest, so I think the range here would be more like 1 in 1,000 to 1 in 25,000. "
• Other things not yet considered in Zvi and Scott's latest posts: (summary - these seem to support as much risk tolerance as Scott, Elizabeth, and Zvi's posts, or even more)
  • Naryan Wong comments on Elizabeth's post with a post from Tomas Pueyo, summarizing: "I think his relevant conclusion looks something like this: Long COVID can look remarkably similar to Chronic Fatigue Syndrome, which REALLY sucks and you do not want to get it, but for a double-vaxxed person who catches COVID, the risks of this kind of outcome are between 0.20%-0.75%."
  • "Your risk of breakthrough covid is probably really really serially correlated. Immunocompromised people make up a huge proportion of breakthrough infections; almost half in one study, despite being like 3% of the population. (Comment on Scott's post from The NLRGSep 4)
    • If they get vaccinated at the same rate as everyone else then, by Bayes' rule,P(bt|ic) = P(ic|bt)P(bt)/P(ic)so that means if 1% of vaccinated people get breakthrough infections each year then vaccinated IC people have about a 1/6 chance of getting covid in a particular year(!); if 10% of vaccinated people get breakthrough infections in a year, then we're looking at more than one infection per year for the average IC person(!!!)the law of total probability or something means that a vaccinated non-IC person has a breakthrough infection risk ofp(bt|~ic) =(1 - P(ic|bt))p(bt)/p(~ic)ie about 0.5% if p(bt) = 1% and about 5% if p(bt) = 10%this is assuming IC people are vaxxed at the same rate as the general population, which maybe isn't true. if every IC person in the US is vaccinated right now, then P(ic|vax) = P(ic)/P(vax) ~= 6% of the vaccinated population. then the IC get infected at a rate of about 8%/yr (at a 1% breakthrough rate) to 80%/yr (at 10%), while the non-IC get infected at about 0.5%-5%/yrthis suggests to me that probably 10% is too high, because otherwise there'd be sensationalistic news articles about Guy Who Got Covid 3 Times After Being Vaccinated and i haven't heard about that at allobviously you might end up immunocompromised in the future, but it's obviously strongly serially correlated. so your estimated lifetime risk should (I think) be a lot closer to whatever you get by cutting your annual risk in half, assuming you're not currently IC, and close to 1 if you arebreakthrough infection risk probably varies with a bunch of other serially correlated stuff like age and sex, too, but i find it hard to believe any of that is going to make a big difference compared to being immunocompromised or not. previous covid infection might matter? but idkall calculations were done before 10 am so i cannot be held responsible for any errors"

Assorted details

• The prevalence of Long COVID after a mild non-hospital-level case is probably somewhere around 20%, but some of this is pretty mild. (Zvi 9/2, citing Scott)
  • His next line is that a percent estimate is ‘kind of meaningless’ but he felt obligated to give one anyway, which I think is net good practice but I’m not sure. What I’m confused by is how he uses the data he reports in this section to end up at 20%, since he quotes studies where (Long Covid percent in Covid group minus Long Covid percent in control group) is respectively at most 28%, 12%, 17%, 13% and 13%, two of which lack a control group. If we naively average that we get 17% minus a few percent for the missing control groups, so maybe 15%. Scott seems to be buying that ‘any symptom at all’ is a reasonable standard here, and that asking ‘did you have Long Covid?’ is ripe with false negatives.For all of these it’s important to note that it’s confirmed seropositives rather than all Covid cases. Most Covid cases likely remain fully undetected. Then again, it’s possible that some of the effects in the control groups could be due to undetected Covid cases.It’s also important to note that Covid cases don’t happen at random, and even when there are controls the controls aren’t checking for health profiles in detail from what I saw on spot checks.The 28% comes from asking if patients have ‘at least one persistent symptom.’ N=234, and the outpatients had a slightly higher rate of Long Covid than the hospitalized patient group. Symptoms that counted included diarrhea, runny nose and ear pain. I don’t know if they were typically mild and they aren’t that big a share of the cases, but that definitely says to me ‘fishing expedition.’
• "Sometimes problems go away after a few months, other times they don’t" (Zvi 9/2, citing Scott)
• "Vaccination probably doesn’t change the per-symptomatic-case risk of Long COVID much" (Zvi 9/2, citing Scott)
  • "That conclusion means it does reduce the per-case-at-all rate substantially, since more of the cases will be asymptomatic if one is vaccinated, on top of being less likely to get Covid at all. This study came out yesterday, and says the risk of Long Covid is cut in half in the vaccinated population versus unvaccinated. My guess is that’s an overestimate, maybe a large one, but that there is some reduction."