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The meetup is over for today.
Hi everybody, it looks like LessWrong made a new account for me in connection with this meetup, rather than using my existing account. Moderators, please put this event under my main account, NormanPerlmutter.
One point that is being glossed over in this essay is that teaching is a difficult skill that is not as strongly correlated with comprehensive expert knowledge of the content than one might think. I say this as someone who worked as a teacher for 6 years.
Part of the process of developing expertise in a field of study is "chunking." The expert mind sees lots of complex things together as a single chunk (which can be unpacked if necessary) whereas the beginner sees the individual pieces. This chunking helps experts to interact with other experts and to apply the material to solve complex problems. But it can actually hinder teaching beginners especially if the expert is not a skilled teacher or has not taught that subject material before. The expert might easily give an overview of the topic, but has to unchunk the knowledge before explaining it to the beginner in detail.
Good teaching requires many interpersonal, and pedagogical skills that are not at all needed for the original learning of the material.
I just downloaded MS Edge so that I could use Bing AI and ask it to find me a Brazillian hammock more than 6 feet wide. After repeated questioning, it kept giving me hammocks less than 6 feet wide (but more than 6 feet long). Even after I pointed out its error explicitly it kept making the same error and finally Bing gave up and told me it couldn't help. Like it would list two possibilities for me, state the length and width of each, and the width was less than 6 feet in each case.
Given all the amazing stuff we've seen out of AI lately, I'm kind of amazed it wasn't more successful. I'm guessing they don't make Brazillian hammocks in that size. (not sure why, as they make Mayan hammocks much wider than that, but anyway . . . )
Is this a blind spot for Bing? Or does Microsoft prefer for it to turn up bad results rather than say that no such thing exists?
Since nobody has called it . . . I spotted the (intentional?) linguistic joke in one of the section headers. The Hebrew word that sounds like Llama means "why."
I've met humans who are unable to recognize blatant inconsistencies. Not quite to the same extent as Bing Chat, but still. Also, I'm pretty sure monkeys are unable to recognize blatant inconsistencies, and monkeys are intelligent.
I agree that this is a risk, but I'm not sure whether it's the main risk. Another risk is that if somebody gets access to the encrypted store, they can use it to steal all your passwords.
I read a lot of Derek Lowe early in the pandemic and regard him highly, but in this case I think he's wrong. Going through the comments of Lowe's post, I came across a link to this essay by a distinguished biologist, Stephen Salzberg, at Johns Hopkins agreeing with Zvi's perspective.
http://genome.fieldofscience.com/2022/10/gain-of-function-experiments-at-boston.html
Salzberg is a computational biologist, not a virologist, but he's a distinguished professor at a prestigious school and does not seem to be on the fringe politically as far as I can tell If anybody knows more about him, please let me know.
Overall, experts seem to be split on this matter. Which is strong enough evidence for me that the research should have been disallowed or at least regulated to the highest security level. The risks are just too great relative to what was learned from the research.
I have written a letter to my representative in the House encouraging her to legislate more restrictions on gain of function research and referencing the article linked above.
This is a fascinating essay that made me think of some of my personal experiences with having my boundaries violated in a new light. Thank you.
You pointed out that just asking for consent can be costly. I think an important social/communication/culture technology to consider is how to make consent requests less costly and/or less frequently necessary, while still allowing a strong social norm around consent.. For instance, having meta-discussions about consent with your friends or meta-rules about consent in your social group or community, that are organized in such a way that asking for consent is seen as easy. Giving close friends broad consent to a wide range of acts, and occasionally checking in on that over time. Etc.
I agree that living conditions are better today than several decades ago and worse today than 3 years ago.
That being said, I have seen a lot of mixed evidence and arguments about long covid and haven't figured out how to best think about it.
I'm confused by your use of "no longer" above. I don't believe we have ever lived in such a world., even before covid. We live in such a world to less of an extent now than we did before. Covid is one more thing that sometimes doesn't turn out ok in the end. But there are many other such thing, including many other diseases.
Thanks.
Could you provide more details on getting Paxlovid? My understanding was that it was only authorized for people with certain health conditions.
I agree that the degree of air circulation within the terminal is an important factor. I'm not certain that the terminal is safer than the plane, but I think more likely than not the terminal is safer.
This link from my previous comment is not exactly a peer reviewed article, but it suggests that the difference in air replacement rate in a well-ventilated versus poorly-ventilated space (the terms they use for mixture of the air, not for air change rate) is only about a factor of 3. Of course, there are different degrees of poor ventilation.
I would be really interested to hear the perspective of somebody with greater expertise in the relevant engineering and physics.
Airplanes do an excellent job circulating air, and are relatively safe places to be. Your risk in the terminal and the taxi greatly exceeds your risk on the plane.
I used to agree with this. But I recently realized it likely isn't true. Consider the following:
- The time to remove an airborne contaminant depends on the Air Change Rate (measured in Air Changes per Hour, or ACH) and how well the air is mixed in the space.
- Air in an airplane cabin has an air change rate of about 13 to 15 ACH. (Actually, the one paper linked in this bullet makes my overall argument pretty well, though it doesn't reference airport terminals)
- Based on this paper, I'd say that an air change rate 0.5 ACH is a fairly low estimate for an airport terminal.
So if the airport terminal is about 30 times less crowded than an airplane (as measured by number of people per unit volume of air), then all else being equal, the risk of covid for each hour spent in the terminal would be comparable to that in the airplane. It's more complicated because the air in the airplane is mixed better than in the terminal most likely. But I think the airplane is actually way more crowded than the terminal, by a factor orders of magnitude larger than 30. Airport terminals typically have high ceilings. Overall, I think the terminal is much safer per unit time than the airplane, even considering the better ventilation on the airplane.
On top of that, the air filtration on an airplane is often turned off while the airplane is sitting at the gate.
Regarding more people declining the second shot than the first shot, my best guess would be that people took the first shot, and either they themselves or one of their acquaintances had an extremely bad side effect, either actual or perceived, so they decided not to take the second shot. I know one person who followed this reasoning. Her husband fell ill after his vaccination with unclear causes, and she attributed it to the vaccine. She finally did decide to get her second shot and booster recently.
Another possibility could be that some financial incentives incentivized the first shot but not the second shot.
Well, the electric eraser was maybe a slight improvement over my manual eraser when I use both together, but not enough to really solve my problem. I went back to using mostly the manual one as it's more convenient.
I just found out that electric erasers are a thing. (Similar to an electric toothbrush, but an eraser.) I have ordered a high-end electric eraser, going to see whether it helps me to do better using my current paper and pencil setup.
Anecdotal, but similar -- when I used to play in chess tournaments, I had a sense that I performed better and made fewer errors when I had more sleep, to the point of aiming for 9 or so hours of sleep the night before a tournament.
Cool idea, I like the historic and low-tech aspect. I will look into it.
I love blackboards, I was a research mathematician for many years and they have a special place in my heart along with a stick of Hagoromo chalk. But they don't fit my purposes here for much the same reasons as dry erase boards -- they erase accidentally and don't allow for small writing.
I'm not familiar with them and am curious to learn more. My main concern would be whether they allow for fine-scale writing and erasing, since I am writing in small print with lines close together and erasing line by line. Is there a particular brand that you would recommend?
How is the older version better than the newer version (other than meedstrom's comment)?
Thanks. This is similar to what I'm looking for, but a bit too small. I'd prefer something the size of an 8.5x11 sheet of paper, but I might give Remarkable a try.
I just quickly browsed this post. Based on the overall topic, you might also be interested in these inconsistency results in infinitary utiliatarianism written by my PhD advisor (a set theorist) and his wife (a philosopher).
I'm curious to learn more about the thesis that caffeine or other stimulant use can completely mitigate the effects of sleep deprivation until 30+ hours without sleep. My own (subjective, anecdotal) experience with caffeine is that occasional (once or twice a week) caffeine use fairly effectively mitigates occasional sleep deprivation if I got say 5-6 hours of sleep the night before as opposed to my preferred 7-8, but is not too effective if I slept less than 4 hours the night before. The more often I use caffeine, the less effective the caffeine becomes, and that furthermore, during periods of time when I use caffeine regularly (say a cup of coffee every day), I get a time several hours after I have my coffee when I have a "caffeine drop" and feel sleepy, so that my overall productivity isn't much better than if I had no caffeine. I haven't tried dealing with this by having several cups of coffee a day. That might work with regard to productivity, but I expect the side effects (jitters, energy/crash cycles, difficulty sleeping, and also reduced sensitivity to caffeine negating the euphoric effect of occasional caffeine consumption) would be quite unpleasant to me.
What was your old job, and what is your current job?
"If we add all the percentage point increases (i.e. how many more percentage points serology positive participants experienced persistent symptoms vs serology negative participants - data from table 2) then we get 20.3%."
I am not sure whether this reasoning is correct. It seems to be dependent on how the symptoms are categorized. For instance, suppose we divided fatigue into moderate fatigue and severe fatigue. The increased probability for each might be 5%, and then you would get 25.3% rather than 20.3%. Or suppose we combined fatigue and poor attention, which are likely correlated. The combined increased probability of "fatigue or poor attention" is likely less than 7.8%, and this would bring you down from 20%.
It seems to me that the best argument against this is that there are less harmful ways to obtain an additional inoculation benefit, through additional vaccination. Either by getting additional shots of Pfizer/Moderna beyond the third shot, or by getting RadVac in addition to Pfizer and Moderna. I would imagine that there is some very large number of Pfizer/Moderna/RadVac vaccinations shots that would have comparable negative effects on health as getting Omicron once (maybe 10 or 100?), and that getting this many vaccination shots would provide much more protection against covid than intentionally getting Omicron.
In the case of Pfizer/Moderna, in my understanding, I don't think it's too difficult to get more than 3 shots, as many vaccination sites do not ask about prior vaccine status. I remember reading a news story about a person who got dozens of covid vaccines in order to collect the government incentives for doing so.
I'm not currently planning to get a 4th mRNA shot in the next couple months (let along 10), but neither am I plan but neither am I planning to intentionally give myself Omicron.
Looks like Zvi just wrote a whole post in response to the healthdata.org update. In particular, January 19 was his prediction of a peak of reported cases, not of actual cases.
This is true to an extent. Unvaccinated people are still able to attend. They just would need to forge their vaccination card. I think this is not particularly hard to do, though it's not trivially easy and many unvaccinated people would not do it for ethical reasons.
Thank you, good explanation. But see also my response to tivelen below.
Healthdata.org (the University of Washington team) released a new projection January 8, projecting that cases in the US (actual cases, not reported cases) peaked January 6. Had you seen this already when you wrote this post, and if not, does it impact your projection of a January 19 peak for the US?
(Edit: added hyperlink)
How is that different from what CraigMichael said? Attending that sort of event is a type of risk compensation.
This is a very helpful analysis. I was independently undertaking a similar analysis, and it's nice to have this for comparison. I hadn't thought to exclude pedestrians, pedecyclists, and other non-occupants, nor of excluding single-vehicle crashes.
I think a some important pieces are missing from this analysis, as follows.
1) The final number, 548, is the number of miles that I must drive to accrue one micromort for all passenger vehicle occupants. But I am more interested in how many miles I have to drive to accrue one micromort for myself. The average (mean) car has 1.5 occupants. Assume that the average (mean) crash of interest involves two cars, and deaths are distributed roughly equally between each person involved in a crash, total of 3 people on average. So you would need to drive or ride 3 times as many miles as claimed by Josh's analysis to accrue one micromort for yourself. A micromort would accrue to any other passengers in your vehicle as well.
(If excluding all accidents with one car, then the assumption of the average accident including only 2 cars is actually off, as some accidents will include more than 2 cars.)
https://css.umich.edu/factsheets/personal-transportation-factsheet (source for average passengers per vehicle)
https://www-fars.nhtsa.dot.gov/Main/index.aspx -- starting point for further honing this factor
2) If a passenger car gets in a crash with a larger vehicle such as a semi truck or a bus, likely the occupant of the passenger car will be injured much worse than the occupants of the larger vehicle. (I didn't look this up but it seems reasonable.) This would bias the results in the opposite direction from excluding motorcycles and pedestrians. More generally, we should be aware of cherry-picking which risk factors we remove from the analysis.
3) Deaths per 100M motor vehicle miles driven stayed approximately constant in a range of 1.0-1.2 per 100 million miles from 2009-2019 but went up dramatically in 2020 to 1.37 deaths per 100M miles (73 miles per micromort) and has stayed at a higher level or even increased in 2021 based on preliminary data.
https://www.usnews.com/news/health-news/articles/2021-06-04/traffic-deaths-increased-in-2020-despite-fewer-people-on-roads-during-pandemic
https://www.nhtsa.gov/press-releases/usdot-releases-new-data-showing-road-fatalities-spiked-first-half-2021
4) Taking out 50% of deaths due to alcohol impairment, so as to account only for the other driver being drunk, seems fine. But I'm less confident that the average lesswrong reader does not drive distracted or drowsy. This seems like an area where we should be careful about being too confident due to self enhancement bias. On the other hand, there are other ways to drive more safely than the average driver. One of the most important of these is maintaining a safe following distance.
5) Depending on the context, we might be more interested in the micromorts per mile of interstate highway type driving in particular. This risk is about half the mortality risk per mile as compared with all driving.
http://www.bast.de/EN/Publications/Media/Unfallkarten-international-englisch.pdf?__blob=publicationFile (assuming "motorways" has a similar meaning to interstate-type highways)
This figure is relevant, for instance, in answering a question such as "What is my risk of highway death from taking a 1000-mile road trip, as compared with my risk of death from covid over the course of the same vacation?"
Josh's analysis mutiplies the initial figure of 91 miles per micromort by a factor of roughly 6.
Jost includes factors of approximately
A) 1.51 for excluding motorcycles, bikes, and pedestrians
B) 1.78 for excluding single-car crashes
C) 1.86 for seatbelt wearing
D) 1.24 for drunk, distracted, and drowsy driving. This is dominated by drunk driving
I would reduce factor A, as I think it's balanced by cases where a passenger car hits a truck. More research on this could be helpful. For now, I'd say to get rid of half of it, make it 1.25
I would get rid of factor B, but replace it with a discretionary safe driving factor (see below)
I would keep factor C
I would keep most of factor D, maybe reduce it to 1.2.
Add (or rather multiply) in the following factors
E) Factor of 3 to account for only micromorts accruing to one traveler, not to co-passengers or occupants of other vehicles. This is based on an average of 3 people per crash, a figure that would benefit from further research.
F) Factor to account for being a safer than average driver (beyond the effect of wearing a seatbelt and not driving drunk). I think that it might be reasonable for especially safe drivers to use a factor of 2 or 3 here (which would be comparable to eliminating single-car crashes plus more). A factor of 10 seems like it would be too much. For myself as driver, I think I would be conservative and keep it at 1, absent further analysis. I am safer than average in some of my driving practices but less safe than average in other practices and skills.
One way to get a start at estimating this factor might be to look at your auto insurance rate and compare it to the average rate for comparable coverage of a comparable vehicle in your state. Insurance companies are in the business of rating risk after all.
G) Factor of 2 if considering only interstate highway driving (or other divided limited-access highways).
I would start with 73 miles per micromort, using the rate from 2020. Overall this gives me
73*1.25*1.86*1.2*3 = 611
611 miles per micromort for each vehicle occupant, or 1222 miles per micromort considering only interstate highway driving, to be adjusted further by a factor of up to 3 depending on one's beliefs about one's relative safety as a driver.
I have not used microcovid much because I am not confident in its predictions and modeling assumptions, or I don't feel they are clearly enough defined to make the tool useful. The change that would be valuable to me (which I have difficultly operationalizing) would be if Microcovid were improved such that I could be much more confident in its modeling assumptions and could use it without having to try to make lots of guesses about which scenarios are well modeled. Maybe it would be sufficient just to explain which types of assumptions make for robust modeling outcomes (maybe this is already somewhere in the documentation). Otherwise, I will continue not to use it.
I think that in general maybe Microvid works well in low-risk situations but breaks down in high-risk situations.
Prior to the recent Omicron surge and post-vaccination, I tended to estimate my covid risks by looking at reported covid case rates in my area, and assuming that as a fully vaccinated person, my risk of getting covid was likely lower than the average person in my area (Ohio), many of whom are not vaccinated, even if I went to restaurants and bars at about the same rate as I did in 2019.
Some examples of my confusion about microcovid's modeling assumptions . . .
Looking at the risk profiles for hypothetical other people, for fully vaccinated people in my state (Ohio):
Average person in your area: 11,000 microcovids
Has 4 close contacts whose risk profile you don't know, in an otherwise closed pod: 6,400
Has 10 close contacts whose risk profile you don't know, in an otherwise closed pod: 19,000
What is the definition of a close contact here? Does this mean somebody who they live with or something like that or just somebody who they regularly hang out with closer than 6 feet? It seems to me that the average person in my area (the mean-risk person since this mean is largely determined by the riskiest people, maybe not the median-risk person) has more or less gone back to normal and would have more than 10 close contacts if you're counting the people they live with, work with, or hang out with regularly. Or at least closer to 10 close contacts than 4.
Microcovid currently predicts that a fully mRNA-vaccinated person with a cloth mask who spends 8 hours in a bar acquires 380,000 microCovids (38% chance of getting covid), assuming that the average person in the bar went to a bar within the last 10 days. (reduced to 240,000 if the average person within 15 feet 10+ feet away rather than 6+ which seems more likely. But why doesn't the model care at all about people 20 feet away?) (As a side note, the default assumption was that most of the people in the bar had the risk of "an average person in your area" which doesn't seem right for a typical bar.)
And furthermore, the risk after 8 hours is equal to the risk after 4 hours, huh? I'd think that in 8 hours more people would be coming in and out, you'd be exposed to more possible infected people.
If this assumption were correct, then over the next week we'd see basically all the bartenders and bar workers here in Ohio getting covid simultaneously. (Or does it just max out at 4 hours so that the covid risk of working at a bar for a week is the same as for 4 hours? That just doesn't make sense.) Even if half or so of these cases were asymptomatic, it would probably be enough that many of the bars would shut down. Seems unlikely, but I guess we could see if it happens.
Likely one of the missing parameters here is the protection from recent infection. I could imagine that the majority of bar workers who haven't had covid in the last 3 months will get it over the next month or so, which wouldn't be enough to shut down many bars.
A one-night stand with somebody who has covid (modeled as kissing for 10 hours) my risk is only 100,000 microcovids. It seems bizarre to me that this risk would be about 1/2 to 1/4 the risk of going to a bar for 2 hours with 15 random people who had been in bars in the last 10 days. Maybe my intuitions are just way off. I suppose at the bar there could be multiple people near me with covid, and one of them might be much more infectious than the average person with covid. But I would think that all of them together wouldn't transmit as many viral particles to me as a single person with covid who I am kissing for 10 hours.
Yes, I agree that this nonstandard definition is a crux for this disagreement. Good analysis.
Hmm, suppose an adult had urinary problems and wetted their bed regularly. Which category would you say that fits into? Or somebody whose parents had named them something that they didn't like and they changed their name and didn't want others to know their original given name due to aesthetic preferences and social implications of character traits related to that name?
There would be some social harm in sharing this either of these, but would it necessarily be adversarial? Even if others were aligned with the person with the secret, they couldn't help but look at them a bit different knowing the secret.
Could you give an example of exploring un-endorsed emotional reactions? How is this related to having deeply held values?
In this case, sharing it with people who don't know her and will likely never encounter her will do minimal harm, so you might suggest that as an exception to the secret keeping.
Another such case is if sharing something would embarrass somebody. They might be embarrassed in spite of others not acting adversarial towards them.
I have been thinking about this topic a lot on my own and with friends before finding this post and was excited to see a post so related to my recent thoughts. One idea that came up in a recent discussion with a friend was that the pitfalls of the reasonable good faith effort in connection with common communication norms, especially if somebody reveals a secret accidentally and is feeling vulnerable and then asks you to keep it secret. In that case, if you say, "I'll make a good faith effort to keep it but I can't promise" it may be interpreted as "I don't care about the privacy of your secret." What the person is actually wanting to hear is something more like "Don't worry, your secret is safe with me." There is a social expectation of some degree of fallibility, and depending on the social context, pointing to this fallibility may overemphasize it and be interpreted differently from how it is intended. All this is very context-dependent.
Are you saying that you agree with William Eden's claim that vaccination does not substantially prevent the spread of covid? Or is that one of the things that you would "quibble" with him on? That point seems much larger than a quibble to me, it's a key point that's being debated currently about public health policy. My own understanding is that while the vaccines are of course not perfect at preventing spread they do prevent spread to a significant degree, and therefore vaccination is indeed a public health issue not just an individual decision.
The 97% was in case there was no other strain that comes in. So maybe the 96% is even taking into account another new strain? Or maybe it was just a typo.
There is an important practical consideration that is being left out here. Attempting to completely devote one's life to these causes in the way described would not necessarily be effective. The best way to devote your life to a cause is not necessarily in a super-fervent way, because that's not how humans work. We need certain types of motivation, we have physical and emotional needs, we suffer from burnout if we work too hard. So if you believe that astronomical suffering risks are the most important issue to work on, then by all means work on them, but don't overwork yourself, it will likely result in anxiety, burnout, and unhappiness, which won't actually help you to work more effectively. Work on these problems, make them your life's work if you see fit to do so, but do so in the context of an overall good life.
I was linking to a news article on CNBC that quoted the CDC director. in the third paragraph. I didn't take the time to track it back to the CDC directly.
For what it's worth, the CDC reported that side effects to the booster are less compared with the second dose, and that was also my personal experience.
If I understand correctly, Zvi's idea is that vaccine protection against infection has likely gone down, but vaccine protection against severe infection has held nearly constant, so that the vast majority of additional infections among vaccinated people will be non-severe.
I am skeptical of the claim that a substantially new risk profile is here to stay for the long term. The best reference case we have for this pandemic, I think, is the flu pandemic from 100 years ago. At that time we had no vaccines for the pandemic, and furthermore the flu mutates much more easily than covid. Nonetheless, the pandemic was pretty much over in two years or so. Not because there was no flu left in the world, but because humans developed enough immunity to this especially virulent flu that it reduced back to the threat level fo the flus that had been around for many years prior. I expect that something similar will happen with covid. Over the next year or two, humans will continue to develop immunity through vaccination and through infection. Technology for covid treatment will also continue to progress. Covid will stick around indefinitely, but after a couple years it will not present too much larger risk than the coronaviruses that have been around for a long time. Maybe a bit larger but not like it is now.
That being said, there is still the question of whether a couple years is too long to wait before returning to a more normal life. I think it is probably too long, and now that I have gotten my booster I am planning to mostly return to a normal life as best I can, as long as Omicron doesn't get too bad. The world at large will not return to normal for a while most likely, but as individuals we can decide what risks we are personally willing to take. Eventually ordinary people and politicians will be tired of all the protective measures and move back to a world substantially similar to 2019, at least in most countries. (My prediction for "eventually" is 75% probability within the next 4 years, 50% within the next 2 years, though I'd have to operationalize the claim better to make that a serious prediction.)
The comparison to the mortality rate of 2005 or 1950 doesn't feel quite right either. That is just looking at the overall mortality rate, but the distribution of mortality has changed as well. I'm fairly certain that compared to 2005 there is way more mortality in developed countries due to infectious diseases that can be spread by asymptomatic people through casual social contact. The particular preventative measures in place are moderately effective at preventing that particular type of mortality. Possibly compared to 1950 as well, though I'm not sure, we've made a lot of progress against infectious disease since 1950.
Would we be better off as a society if we dropped the covid prevention measures and focused all those resources on preventing other causes of mortality such as cardiovascular disease? Quite possibly so, but unfortunately we're not well enough coordinated to do that.
I have decided to get my booster of the Pfizer vaccine and am scheduled to get it on Monday, November 29, the soonest day that was acceptably convenient with regard to my concerns about side effects the next day.
Reasons for the decision were as follows. I'm fairly confident that I'm making the correct decision to get a booster very soon. I'm less confident as to whether I'm choosing the best booster, but I don't think that's likely to make a big difference.
Decision to get a booster very soon
The new Omicron variant increases my risk from covid over the time frame of the next few months. I want my booster to have a substantial effect before Omicron becomes highly prevalent in the US. This was my main motivation to act very soon. I had been tentatively planning to get a booster within the next week, but may have put it off for longer before learning about Omicron.
I learned about original antigenic sin, which makes the concerns about waiting for a vaccine specific to new variants less relevant.
The CDC reported yesterday that covid boosters have less side effects than the second shot, which reduces the credence of the hypothesis of a lifetime limit on mRNA vaccines and also reduces my short-term concern about dealing with the side effects of the booster.
Decision as to which booster to get
Since I now want to get a booster very soon, the possibility of traveling to get a booster not available in the US is no longer appealing. And the risks of traveling are greater due to Omicron as well.
Convenience -- the first place where I went to book a booster (Walgreen's near my house) only allowed me to get a booster of Pfizer since my original vaccine was Pfizer. (In reality, this may have been the biggest reason.)
Getting a booster of the same vaccine as the original is the generally accepted establishment medical advice (based on Walgreen's requirement and also my doctor's advice).
The study referenced in this comment shows weak evidence that a Pfizer or Moderna booster after first two shots of Pfizer is more effective than a J&J booster. But Moderna might be the most effective of all.
Getting the same vaccine as I have already gotten in the past is dealing with something that's more of a known quantity to my body. It seems less likely that I would have unusual side effects with the same vaccine as compared with a new vaccine that I haven't tried yet.
Getting a booster of the same vaccine puts me in a more widely studied cohort, as noted here which might means I'll have more information relevant to my situation going forward than if I boosted with a different vaccine.
I have some thoughts that it might be better to get a J&J booster anyway since it is less likely to hit the lifetime maximum mRNA issue, or because it might do better in stimulating other areas of the immune system besides antibody production, but that is balanced out by the reasons above.
After a bit of research, I did not find any articles about a lifetime limit on mRNA vaccines. [Edit 1 -- found an article. See section 3.2.2.1. But it's an expert opinion submitted in connection with a lawsuit] [Edit 2 and the authors are affiliated with an anti-covid-vaccination group so has a stronger likelihood of bias as compared with a journal article. So it is likely quite biased.]