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Note: It usually takes me quite a while to write and publish anything online, but this seems pretty pressing so I've done it in a hurry. Please excuse any omissions or mistakes and feel free to yell at me about it in the comments.


TL;DR: (If not for this post), I predict that the median EAG London attendee will be less COVID-cautious than they would be under ideal epistemic conditions* and under their own values.

*Ideal epistemic conditions means something like "if they were better informed about the current state of affairs vis-à-vis COVID in London and any other relevant descriptive facts, and thought long and hard about how much risk they'd like to incur given the costs and benefits of various interventions like masking, social distancing, and getting a last-minute booster." It does not mean "if they had same degree of risk tolerance as me or as I'd like others to have."

Point 1: case rates in London are likely higher than you think

Relevant info from the UK Office for National Statistics

The subtitle just above links to a report that was released two days ago on April 8, 2022. 

  • In England, the percentage of people testing positive for coronavirus (COVID-19) remained high in the week ending 2 April 2022; we estimate that 4,141,600 people in England had COVID-19 (95% credible interval: 4,033,600 to 4,249,500), equating to 7.60% of the population or around 1 in 13 people.


  • In the week ending 3 April 2022, the Omicron BA.2 variant remained the dominant variant across all UK countries; the percentage of people with infections compatible with the Omicron BA.2 variant remained high in England and continued to increase in Wales, however the trend was uncertain in Scotland and Northern Ireland.

More concisely, it looks like almost 8% of the English population had COVID as of April 2.

According to Our World in Data, the UK and the US had pretty similar confirmed new case numbers until about March 1, when the UK's case rate started climbing but the US's did not. 

Anyway, the point is that the UK positive rate looks to be about seven times the U.S. rate. For those of us flying in from the U.S., then, our day-to-day impression of how things are going at home is probably misleadingly benign. 

Point 2: people have kinda stopped giving a shit

Until about a week ago, so had I. Then I:

  1. Read that case rates on Georgetown's campus were increasing a lot
  2. Realized that it would be bad for anyone in the GU group to get COVID and either (a) find out and stay home or (b) not find out, go to London, and risk passing it on to other EAG attendees, and
  3. Assumed the role of the grumpy COVID hawk and ordered our group a bunch of rapid tests on Amazon for just over $7 a pop (or <1% the cost of a DC<->London rountrip flight) which were delivered the next morning.

I think the two takeaways from this story are best conveyed via meme:

It ain't 2021 no more

More generally, I have the pretty banal impression that (at least among EA's typical demographics) preventative measures like masking, frequent rapid testing, active  ventilation, and further vaccination have largely fallen by the wayside. Given the state of the world (e.g., low case rates, Paxlovid) now, this makes total sense and I'm not condemning it. 

But I am trying to point out that this limits the inductive validity of extrapolating from the epidemiological outcomes of previous in-person EA consortia  how useful it is to conclude from the success of 2021-early '22 EA events that everything is going to be fine. 

Maybe it will be fine, I don't know, but we're out of sample here! Never before has there been such a large EA event in a city with such a high COVID-positive rate with attendees from around the world, many of whom haven't been doing much to mitigate viral transmission these last few months.  

Something about individual or total COVID risk changing dramatically for groups made of individuals whose risk of catching and/or spreading the virus is correlated with one-another thanks to math

I don't have the time to figure out how to present this idea accurately and concisely, but I'm pretty sure the following thing is true:

Suppose in world  people each of whom have a probability  of having COVID get together in a group in such a way that the probability of transmission from one infected person to a non-infected person is   (where  depends on things like masking and ventilation) and this results in each participant having a probability  of ending up with COVID. 

Now suppose in an otherwise-identical world , each person begins with a probability  of having COVID (i.e., 1% more likely than in world ). Then at the end of the event each person has a probability  of having COVID, with  for large .

(It's not a quote; the formatting just makes it look nice)

If anyone wants to clarify what I'm trying to get at here or link to something good on the matter, I'd be very grateful!

What we can do about it

1) Get another booster (if you decide it would be wise)

I'm guessing the single "best" (i.e., most individually and altruistically protective) thing to do is to get a booster by the (end of the) day after tomorrow, April 11. In the U.S., second boosters aren't approved by the FDA for most people under 55. But, to be frank, I think it is ethical, easy, and not legally risky to get one even if you're not in this category. For more about second boosters, check out Zvi's post

2) The usual spate of non-pharmaceutical interventions

Hey man, I don't like wearing N95s either, but they seem good for reducing your risk of transmission and infection! Same with frequent rapid testing, ventilation, social distancing, the whole nine yards. I haven't thought about it enough or done enough research to make a normative claim here, but I will make the utterly banal descriptive claim that doing this sort of thing will reduce the expected number of COVID cases caught at EAG. 

3) Figure out what set of things a reasonable EAG attendee should actually do and write about it on the Forum

One of EA's unusual advantages is that it has a laughably high concentration of extremely smart and numerate people with a good understanding of epidemiology and/or quantitative modeling. So, go make this post look like a second grader's crayon scribble next to one of these hyperrealistic masterpieces by figuring out in more detail how worried we should be and what the best practical risk-reduction options are. Your fellow EAs will thank you!


Final note: I may update this post in the next 1-2 days with additional information. Any substantive changes will be labelled as such :) 





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At the start you say you are going to argue that "the median EAG London attendee will be less COVID-cautious than they would be under ideal epistemic conditions". So, I was expecting you to discuss the health risks of getting covid for EAG attendants (who will predominantly be between 20 and 40 and will ~all have been triple vaccinated) . Since you don't do that, your post shouldn't update us at all towards your conclusion.

The IFR for covid for all ages is now below seasonal flu. The risk of death for people attending EAG is extremely small given the likely age and vaccination status of attendants. 

It is difficult to work out the effects of long covid, but the most reasonable estimates I have seen put the health cost of long covid as equivalent to 0.02 DALYs, or about a week. (I'm actually pretty sceptical that long covid is real (see eg here))

For people aged 20-40 who are triple jabbed, the risks of attending EAG are extremely small, I think on the order of getting a cold. They do not justify "the usual spate of NPIs"

There's also the point that covid seems likely to be endemic so there is little value in a "wait and see" approach

I imagine the costs are higher for people who might miss flights, even if health costs are low!

Eli from the EA Global team here: For anyone that has travelled to London for the conference, we will reimburse you for any extra travel or accommodation costs that arise should you be stuck in town due to contracting COVID-19 (e.g. if you have to stay in your hotel for an extra week and book new flights due to contracting COVID-19 at or slightly before the event).

You can see more information in our COVID protocol here, though please feel free to reach out to hello@eaglobal.org should you have any questions or concerns — thanks!

What fraction of EAG attendees do you expect to miss flights because of COVID if the event proceeds as planned?

Oh, interesting forecasting question!

1400 EAG attendees. Currently about 7.5% in England have Covid, but if someone's not symptomatic and not testing positive on an LFT they'd be much less likely to be Covid positive, so assume 1% of EAG attendees have Covid (14 attendees).

How many people will these 14 asymptomatic attendees infect? If no one were vaccinated and they were symptomatic, it could be something like 8 people each, but of course they'll be less infectious and others will be vaccinated so perhaps they each infect 1.5 others on average.

So perhaps 21 people catch Covid at the conference. Of that, the majority are probably from the UK, so wouldn't miss a flight. It also can take several days from initial exposure to developing symptoms and testing positive, so people flying out on Monday are perhaps less likely to miss their flight (though it's still possible!).

Overall I'd predict 0-7 people miss their flights from Covid if EAG goes ahead as planned (my best guess is 2 people).

Note that I did no research for the above, but I hope all my assumptions are listed clearly enough that anyone could replace them with their own numbers!

Edit: Already caught one mistake where I didn't carry my numbers through properly lol, fixed that

Your forecast seems plausible to me but on the lower end of what I'd have thought. 

Attending a conference probably implies a lot more social mingling than the average Londoner is doing.

If a lot of vaccinated people are asymptomatic (at least initially) and LFTs aren't very sensitive, would we expect a factor 7.5 reduction of conference attendees? I don't have the figures to compare this with, but for instance, a factor of 5 doesn't feel obviously wrong.

You say if no one were vaccinated, around 8 people would be infected on average? That seems low and like you went with the R0 of omicron in an unvaccinated population. But again, people are attending a conference. In a conference setting, even just one superspreader among the 8 people could infect >100 people if they were unvaccinated. I do think superspeaders are less likely in a triple-vaccinated population, but omicron ba.2 seems to be pretty undeterred by vaccination in some ways.

Incubation time is frequently <2 days with omicron, so you may have some people who get it at reception and infect more people on the last day of the conference. (I haven't looked up whether the conference lasts 2.5 days or just 2 days, so that may also be relevant.)  (On the other hand, some people may stop attending the conference once they feel unwell or if they take a second test and it's now positive.) 

FWIW, at the last EAG I saw people go to a crowded restaurant and then go back to the conference. If that's done on the last day, it doesn't matter. If it's done on the first day, it may lead to more new infections.

Overall, I think  >5% of attendees infected doesn't seem  implausible to me, but I would also put some probability on your number at the lower end.  (With the nice weather, if people do most of their one-on-ones outside, I think that would reduce the risks by a lot!)

I also expect that the accounting will be complicated because of EAG afterparties or after events. Probably those will be riskier than the conference but the people who attend may already have had one of the omicrons and therefore be pretty safe, or they may not care about getting infected because they're back to living life normally and EAG isn't an inconvenient time for them to catch it. 



This also seems like reason to encourage people to lobby their governments to get rid of testing requirements for travel

Thank you for the answer! Strongly upvoted.

It is difficult to work out the effects of long covid, but the most reasonable estimates I have seen put the health cost of long covid as equivalent to 0.02 DALYs, or about a week.

Could you share these?

I think this is probably about right in terms of direct health costs and direct loss of productivity (due to brain fog and/or chronic fatigue), but after a few years of long COVID, I'd also worry about whether you'd still be an EA if/when you do recover and how much it would derail the rest of your career. And some people could end up with long COVID for decades; we don't know how long it can last.

I put the risk of debilitating (1+ year?) long COVID conditional on catching COVID (Omicron, fully vaccinated and boosted, relatively young) at around 0.2% based on this post and my own comment using the same figures but a more direct estimate of severe risk. Maybe lower for young and healthy people and higher for older people or people with health conditions.

So 0.2% * 52 weeks = 0.1 weeks, and then multiply this by the number of expected years long COVID lasts + indirectly derails (maybe adjusting for how much it derails your life). This is also just for the severe tail risk of long COVID, so excludes shorter term risk, like days lost due to acute infection and long COVID resolving within (?) a year.

Note furthermore that differences in precautions will affect how often you get COVID and take on this long COVID risk, in expectation.

I'm actually pretty sceptical that long covid is real (see eg here)

There's a thread here on this. I think it's probably real, and the worst cases are unlikely to be psychosomatic, although some may be misattributed. Also, that something is psychosomatic isn't very reassuring anyway.

There's also the point that covid seems likely to be endemic so there is little value in a "wait and see" approach

You can still respond to risks, cases are relatively high now in particular, and we actually don't have much data on the Omicron (or BA.2 specifically) and long COVID.


All this being said, my tentative views are 

  1. People should mostly do whatever they want at this point and take on their own risks. If you want to avoid COVID (get it less often; avoiding it forever seems pretty costly), get good masks (at least N95/KN95) and limit the number of people you interact with maskless (indoors), especially when cases are high. Feel free to attend EAG with a mask.
  2. Wearing a mask seems very low cost in many settings, so I personally think it's often worth doing.
  3. However, cutting against 2, if you half-ass your precautions too much (and I don't know where the line is), you'll just get COVID about as often as people who don't even bother with precautions and you may take on additional costs and miss opportunities in doing so. If you're trying to reduce how often you get COVID, an important source of risk can be the people you live with.
  4. There are probably better things to focus on for productivity than COVID for someone who is young, healthy and fully vaccinated + boosted. Exercise, diet, productivity coaching, etc.. There may be other infectious diseases to consider, too (e.g. Lyme).
  5. It's better to get COVID when your immunity is highest, e.g. 2 weeks-X months after your most recent shot. (I'm not sure what X is.)

(I'm actually pretty sceptical that long covid is real (see eg here))

That's an interesting paper. But unless I'm missing something, Table 2 shows that fatigue was more common in the group with positive serology result than in the group with negative serology result: 7.7% vs. 2.7%. Also, among the people with a negative serology result, only ~0.2% thought they had covid-19 and also reported fatigue, and it may be the case that many of those people actually did have covid-19 (and their serology result was false negative).

(BTW it's weird that they did not include loss of smell or taste in the study...)

The strongest piece of evidence I'm aware of for the risk of long-term brain-related damage from covid-19 is this Nature paper.


It's table 3 I think you want to look at. For fatigue and other long covid symptoms, belief that you had covid has a higher odds ratio than does confirmed covid (but no belief that you had covid). 

I think there is good reason to be sceptical of long covid. It groups together multiple different symptoms that are strongly psychologically influenced and already prevalent in the population, such as brain fog and fatigue. In a pandemic where anxiety about disease is high and social interaction low, we should expect people to attribute these symptoms to covid. 

Another point I find useful when thinking about this is that if some of the more dire predictions of the effect of long covid, such as 1% chance of having your life ruined, that would be visible in plain sight - lots of sports stars and celebs would have to retire. I have checked and I know of zero cases of professional English footballers retiring due to covid, but we would expect several to have done so if long covid risk were really that high. 

It's table 3 I think you want to look at. For fatigue and other long covid symptoms, belief that you had covid has a higher odds ratio than does confirmed covid

That's exactly what we should expect if long covid is caused by symptomatic covid, and belief-in-covid is a better predictor of symptomatic covid than positive-covid-test. (The latter also picks up asymptomatic covid, so it's a worse predictor of symptomatic covid.)

You're right I didn't make a full, airtight argument, and that severity of infection is indeed a crucial consideration. My extremely unqualified impression is that: 

  • Long covid is real but no longer the main source of expected disvalue for the 3x-vax'd
  • A non-trivial number of 3x-vax'd people (20%?) who catch covid lose more than half productivity and/or quality of life for 4-21 days, and this is where most of the expected disvalue comes from

This is what my brain has decided on after being exposed to a bunch of unstructured information so the error bars are very large, and I should probably update toward your POV

 I think the OP is compatible with the view that this isn't about Long Covid. It sounded like the OP thinks infection will be super likely at EAG even with precautions given that 8% of Londoners have the virus and given that people will be mingling a lot. I think the OP also expects that some EAs are unaware of how high the risk is. Basically, if you thought going to an event was >20% likely to give you the flu, would you attend?

(>20% isn't my prediction; I'd have to think more about it [edit: I gave a very vaguely stated range below khorton's forecast]. It's my interpretation of the sentiment in the OP. FWIW I I disbelieve your estimates and general sentiment about Long Covid.) 


The OP didn't make any arguments about the health risks, so one cannot infer his stance about long covid from the post. As I intimated in my comment, I don't think omicron is as bad as flu, I think it is as bad as a cold. Yes, I would attend if there were a 20% chance of getting a cold. The additional covid risk makes almost no difference to the background risk of attending the conference and is swamped by other risks, such as the risk of a nuclear strike on London or being in a traffic accident on the way to the venue. 


On long covid - what is your view on the paper I linked to which suggests that long covid is psychosomatic? 

I haven't looked into any papers in detail. I've read multiple EAs commenting on various papers and there seems to be ambiguity on how to interpret them. For instance, I remember someone (Katja Grace?) pointing out how the following points are statistically compatible: 

  • Long Covid affects a significant portion of people
  • Among people who thought they had Covid because they recently started suffering from a mysterious chronic illness, seropositivity is lower than the baseline

That's because there are indeed other causes of chronic illness that could be driving the belief "I probably had Covid." 

Another option is that Long Covid messes with seropositivity – I think I saw that hypothesized as well. It might be a somewhat conspiratorial hypothesis, but "Long Covid is psychosomatic" sounds just as conspiratorial. We know that post-viral syndromes exist and we know that SARS-1 led to extreme long-term issues (though this is highly confounded by disease severity).

I also don't think it would help much if the mechanism was psychosomatic. That doesn't change the problem that people cannot work anymore. (I guess you're thinking that if you believe it isn't a problem, you can make yourself immune? That may not work if you're only 75% confident in the hypothesis. Illnesses can lower the clarity of one's thinking and make you more anxious.) 

In any case, I think there's so much anecdotal data with Long Covid (even just in EA-related or personal/family circles) that anecdotes are useful here, so I've built up a picture that feels more robust than heavily contested studies based on self-reports. Of course, if all the studies said Long Covid wasn't a thing, I'd believe them. It's just that combined with priors I got from anecdotes, my interpretation of various studies is likely to be somewhere in the middle, rather than at the extremes.

That said, I also think we can probably rule out Long Covid rates (for >3 months out) >0.8%. In particular, I think we have some evidence from reports about athletes getting sick early on in the pandemic, and very few reports of "famous athlete can no longer play soccer because of Long Covid." (It's more common in women, though, and I mostly saw coverage of male athletes at the time.) (Edit: I googled soccer players with Long Covid and found quite a few results as well as statements saying very few professional players have even caught it, so I changed my estimate again from >0.5% to >0.8%.) 

Edit to add: You estimated the expected health costs of Long Covid at about 1 week in your original comment. I think my view isn't too far away from that (maybe I'd say it's twice that). I was mostly reacting to "I doubt it's even real" part of your comment. 

Another approach: According to the Zoe Covid study, 280,000 people in the UK got Covid today. That's 0.4% of the UK. So if that's the baseline for one day, we get a 1% baseline for the 2.5 days of the conference. 

I assume that EAs take more tests than the average person (esp. now that tests have scaled back) but that attending a conference is substantially more risky than the average behavior. I probably expect there to be more than 1% infections during EAG for that reason, but maybe not a lot more? With the 1% prior/anchoring, I'm thinking >5% is a bit too high, so I now put less than 25% probability mass on that. But my median is well above 1%. 

Is the source of this graphic public? This affected my perspective a lot and it'd be great to have a clean copy. :) 


thanks pablo. yeah sorry I couldn't access the Financial Times page directly

There were tons of cases from EAGx Boston (an area with lower covid case counts). I'm one of them. Idk exact numbers but >100 if I extrapolate from my EA friends.

Not sure whether this is good or bad tho, as IFR is a lot lower now. Presumably lower long covid too, but hard to say

Thanks very much for writing this.

It's also worth noting that for many international travelers catching covid may prevent you from being able to go home.

My guess is many people will not want to be masked for much of the conference. However, it might be worth considering a pro-masking norm during lectures. During these the audience isn't generally talking or eating, so the costs are lower than in a 1-1, and the benefits are higher because so many people will be in the same room.

People could also consider bringing (or CEA could provide) nasal sprays.

I'm surprised this comment was that controversial! I thought it was one of my more milquetoast. 

FWIW my guess is it's because people don't want to wear a mask during lectures and/or think that's a bad norm. 

(I didn't downvote your comment.)

I'm also surprised as it makes quite an important point that hasn't been made before and I find it's fair to suggest introducing some minor inconvenience for everyone to avoid major inconvenience (not being able to travel home when planned, etc.) for a non-neglectable number of people.

(FWIW regarding your concrete suggestion: I agree that having to wear masks during lectures seems very low cost. It also seems to be quite low benefits, though, as you're much more likely to get infected during informal interactions while talking to people than during a lecture.)

I had not heard about nasal sprays being possibly useful. Sounds like there's preliminary in vitro evidence and a couple of case studies: https://www.biorxiv.org/content/10.1101/2020.12.02.408575v3.full https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7645297/ Though I'm confused about why there isn't more evidence either way given the first info came out in 2020.

AFAIK there is one positive, randomized trial for a nasal spray containing Iota-Carrageenan (Carragelose):  "The incidence of COVID-19 differs significantly between subjects receiving the nasal spray with I-C (2 of 196 [1.0%]) and those receiving placebo (10 of 198 [5.0%]). "  It is available at least in Europe, and in the UK I think under the brand name Dual Defence.  Why it has not received more attention is beyond me. 

Perhaps CEA could buy some and have them on offer at check-in? 

Will there be Covid tests available at EAG London? (Ideally everyone should be testing every day of the conference - Fri, Sat, Sun).

Eli from the EAG London team here: there will be plenty (hundreds) of COVID tests available at the event for any attendee who wants them. Please ask an on-site volunteer or organizer if you'd like a rapid/lateral flow test!

I was wondering if someone was looking into far UVC devices. I did briefly and it seems they're rare and maybe only available on a B2B basis. Also, I'd guess someone is currently working on a post about how EAGx Boston caused some higher-than-expected number of cases, so there's an update in favor of extra caution there. 

I think nobody has a doubt that all EAG attendees who don't take precautions will get exposed to at least one covid-positive person.

I think the main question is how much to care about that (compared to the alternative).

Does anyone disagree?

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