A year and a half ago, I wrote a post called Covid-19: My Current Model. Since then things have often changed, and we have learned a lot. It seems like high time for a new post of this type.

Note that this post mostly does not justify and explain its statements. I document my thinking, sources and analysis extensively elsewhere, little of this should be new.

This post combines the basic principles from my original post, which mostly still stand, with my core model for Omicron. I’ll summarize and update the first post, then share my current principles for Omicron and how to deal with and think about it.

There’s a lot of different things going on, so this will likely be incomplete, but hopefully it will prove useful. The personally useful executive summary version first.

1. Omicron has already taken over, most cases are being missed, crunch time is now. Crunch time will likely last 1-2 months.
2. First two shots don’t protect against infection, boosters do somewhat (60%?).
3. Vaccination and natural infection protect against severe disease, hospitalization and death (best guess ~80% reduction in death for double vaccination, 95%+ reduction in death for boosters but too soon to know).
4. Tests work, but when delayed are mostly useless for preventing infection especially when delayed, as Omicron can spread within 1-2 days after exposure. Rapid tests mostly test for infectiousness, not being positive.
5. Omicron probably milder than Delta (~50%) so baseline IFR likely ~0.3% unless hospitals overload, lower for vaccinated or reinfected.
6. Being young and healthy is robust protection against severe disease and death, being not that means a lot more risk. Long Covid risk small but real for all age groups, vaccination likely helps a lot.
7. Medical system is under strain, could be overwhelmed soon, should be better again in a few months at most if it gets bad. Delaying infection has value but stopping it fully is likely not worth the cost. If you care about real prevention, the tools that matter are vaccination, good masks (N95 or even better P100+), social distancing and air ventilation.
8. Vitamin D and Zinc, and if possible Fluvoxamine, are worth it if you get infected, also Vitamin D is worth taking now anyway (I take 5k IUs/day). Paxlovid is great (~88%) if available right after you test positive, but in very limited supply for now.
9. Default action on positive test is 5 days isolation at home as per new CDC guidelines, if possible is good to get a negative rapid test before ending isolation. If things get bad, especially if you have trouble breathing, call your doctor, seek treatment and so on.

Here are the old principles that still apply, with adjustments as appropriate:

1. Risks follow Power Laws. Focus on reducing your biggest risks.
2. Sacrifices to the Gods are demanded everywhere. Most intervention effort treats Covid-19 as a morality in which the wicked must be punished, rather than aiming physical interventions to achieve physical results.
3. Governments Most Places Are Lying Liars With No Ability To Plan or Physically Reason. They Can’t Even Stop Interfering and Killing People. There is a War, and the WHO, FDA and CDC, and most similar agencies abroad, and most elected officials, are not on our side of it. Instead they focus mostly on getting in the way, protecting their power and seeking to avoid blame on a two week time horizon.
4. Silence is Golden. Talking or singing greatly increases infection risk, and the directions people face matter too. You’re still not safe or anything, but it helps.
5. Surfaces are Mostly Harmless. Mostly don’t worry about them.
6. Food is Mostly Harmless. Mostly don’t worry about it.
7. Outdoor Activity Is Relatively Harmless. It’s a huge relative risk reduction.
8. Masks Are Effective. I’m less excited about cloth masks than I used to be, but I remain confident in N95s, and if you actually need to not get Covid-19 you can step up and use P100s or other heavy-duty options at the cost of social awkwardness. My rule of thumb at this point: Cloth masks are for satisfying mask requirements. N95s are for reducing Covid-19 risk. P100s are for actually attempting to prevent Covid-19. Choose your fighter.
9. Six Feet Is An Arbitrary Number. There’s still nothing better than an inverse square law, so by default I presume 12 feet is a quarter of the risk of 6 feet, and 3 feet is quadruple the risk, there is no magic number. No one seems to care about distancing much anymore. If there was one big omission last time, it was not focusing on air ventilation and flow.
10. Partial Herd Immunity Matters. 75% immunity no longer cuts it under Omicron, but every little bit helps. This isn’t an all-or-nothing situation. Every person that is immune, or even partially immune, slows the spread.
11. Yes, We Know People Who Have Been Infected Are (Largely) Immune. This is less absolute than it used to be. Infection by Delta or earlier strains provides strong protection against severe disease, hospitalization and death, but not total protection, and it provides far less protection against infection.
12. Our Lack of Experimentation Is Still Completely Insane. Yes.
13. We Should Be Spending Vastly More on Vaccines, Testing and Other Medical Solutions. Yes.
14. R0 Defaults In Medium-Term To Just Under One. This is true because case rates and behaviors and rates of previous infection adjust until it becomes true. It’s importantly not true if pushed past its breaking point, and the question is whether or not this happened with Omicron. But in a few months, it will be true again either way.
15. The Default Infection Fatality Rate (IFR) Is At Most 1%. Still true, but my estimates are now doubly lower for better treatments and Omicron being milder, see the new section.
16. Many Deaths and Infections are missed. The numbers I put here no longer apply, and the rate at which cases are missed varies a lot based on conditions. My guess is that most deaths are now identified in the United States, but that most cases are once again being missed under Omicron because they’re milder and testing is once again in short supply.
17. People Don’t Modify Behavior Much In Response To Rules. Most of the reaction to conditions is private choices on how to react. Private reaction to Omicron happened despite not much public imposition of new rules. Vaccine mandates are the one big exception.
18. It’s Out of Our Hands. Almost entirely true at this point. It’s on individuals to react wisely.
19. Support Longevity Research. If you think that people dying is bad, maybe we should do something about it.

Next, how to personally think about Omicron beyond the above.

First, infection.

1. Importance of air ventilation is the biggest thing I didn’t talk about before. It makes a huge difference to risk of infection whether or not there is good air flow. The glass barriers in restaurants are probably counterproductive (and my not realizing this early on was a mistake on my part).
2. You are probably going to get Omicron, if you haven’t had it already. The level of precaution necessary to change this assessment is very high, and you probably don’t want to pay that price.
3. You can probably guard against Omicron if you want to do so badly enough and don’t need to work outside the home, either short term or entirely. This means a P100-style or better mask, if you’re actually trying. It means extreme social distancing and isolation and caring about ventilation. It also means getting vaccinated and boosted. For those who are immunocompromised or otherwise at extremely high risk, this is a reasonable option.
4. There are a ton more cases out there than are being reported. Hard to tell exactly how many, but it’s a lot more. In addition to missing a lot of cases, being several days behind can mean you’re at several times more risk than it otherwise looks like at any given time, until things stabilize. So looking at current positive tests can be an order of magnitude or more too low.
5. Omicron spreads easier than Delta even among the unvaccinated. We don’t know this for a pure fact yet but it seems very likely to be a large effect. Assume the amount of exposure it takes to reach critical mass has gone down.
6. Vaccination with one or two doses of current vaccines is minimally protective against infection by Omicron. The data isn’t fully in, but this seems clear. If you haven’t been boosted, your protection is mostly against severe disease, hospitalization and death, rather than infection, although you’re somewhat less likely to spread the disease further because you’ll recover faster.
7. Vaccination with three doses is protective against infection by Omicron, but less protective than vaccines were against Delta. As a rule of thumb I am currently acting as if a booster shot is something like 60%-70% protective against infection but I don’t have confidence in that number. The main protection is still against severe disease, hospitalization and death.
8. The generation time (serial interval) of Omicron is lower than Delta. Someone who is infected today will often be highly contagious the day after tomorrow, and may be infectious tomorrow. Much of infectiousness proceeds symptoms.

Next, testing and isolation.

1. PCR tests are useful and accurate, but don’t mean you’re not infectious, and if they are delayed they become useless. The ideal is getting it back in 24 hours, but even that is a lot of the window before someone is infectious, so this doesn’t provide that big a risk reduction against Omicron. If it takes 48+ hours, use other than for treatment is greatly reduced.
2. Rapid tests are useful and mostly tell you if you’re currently infectious. They can have ‘false’ negatives, and actual false negatives, mostly because you can be infected but not infectious, and then you’ll mostly come back negative. Also user error is always an issue. Rapid tests are the more useful way to identify who is infectious and prevent spread, but far from foolproof.
3. All rapid and PCR tests detect Omicron. I include this because I know of people who aren’t confident on that and are freaking out a bit.
4. A negative rapid test should be necessary before ending isolation. The CDC’s new guidelines don’t say this but this seems overdetermined and obvious to me. If you care about not being infectious, you should check on that before exposing others.
5. The majority of infectiousness is within the first five days, and CDC guidelines now only require five days of isolation. That doesn’t mean five days is suddenly safe instead of unsafe, but the show must go on, so the rules have changed. Five days plus a negative test seems fine in general, but I still wouldn’t visit any grandparents that soon.

Next, vaccination, prognosis and treatment.

1. Omicron is probably substantially milder than Delta. My guess is something like 50% milder, so half the risks. How much comfort that provides is your call.
2. Being young is still the best defense. Everyone please stop being terrified about what might happen to young children. Most deaths will still be among the old and unhealthy. Remember that these are orders of magnitude differences.
3. Being healthy still helps a lot. If you are at a healthy weight and don’t have diabetes, and aren’t immunocompromised, those are also big games. If you do have these issues, that’s a problem. See my old post on comorbidity.
4. Vaccination is highly protective against severe disease, hospitalization and death. The vaccines are likely somewhat less effective against Omicron than Delta here, but still highly effective. Protection against hospitalization is probably something like 80%, with likely additional protection above that against severe disease, and then even more protection against death.
5. Booster shots are even more protective. I urge everyone to get their booster shots.
6. Previous infection, including by Delta, is highly protective as well. It’s at least similar to being vaccinated normally. Unclear if it’s better than that.
7. The risks of Covid-19 prevented by vaccination greatly exceed the risks of vaccination. Even the specific ‘risks’ of vaccination are net decreased by vaccination, because it prevents Covid-19 and makes Covid-19 more mild. If you are worried about unknown risks, get vaccinated. There are a few exceptions for specific medical situations, if you think you’re one of those exceptions talk to your doctor.
8. Most cases will be asymptomatic or mild, even if you are unvaccinated. It’s important not to forget this, or pretend otherwise in order to scare people.
9. If you do have symptoms or test positive, take at least Zinc and Vitamin D. You should be taking Vitamin D regardless. This isn’t a statement that you shouldn’t take anything else, but there’s nothing else that I know rises to this level.
10. If you test positive, consider Fluvoxamine. It is an SSRI, so it’s not something one should take lightly or proactively, only when you know you’ve been infected. Again, I’m not saying not to take anything else that I’m not listing, I’m merely saying I don’t have this level of confidence in anything else that’s available. Merck’s pill increases risk of mutations and I now believe it should not have been approved, but it likely is good for your personal health outcomes if you can get it in time and adhere to the protocol. If you do take it, you really really really need to follow the full protocol exactly.
11. If you test positive and can get it in time, take Paxlovid. Paxlovid reduces hospitalization and severe disease by about 88%. If you’re young and in good health and don’t want to take from the currently limited supply, I applaud that decision until there’s sufficient supply.
12. By default, recover while isolating at home. The medical system is there if you need it, but most of the time you will not need it. Trouble breathing is the biggest ‘seek treatment now’ sign, but I am not a doctor, this is not medical advice, and when in doubt call a real doctor.
13. Once you go to the hospital or otherwise seek treatment, I don’t have anything for you beyond wishing you luck. If I get sick, I will follow my wife’s advice, as she is a doctor. Can only focus on so many questions at once.
14. If the hospitals get overloaded things get much worse. A lot of patients that would otherwise live, will die without treatments the hospitals can give, especially oxygen.
15. Getting Omicron in January (or late December) is worse than getting it in February, which is worse than getting it in March. At some point in January (or maybe February, but probably January) there will be a turning point where strain on hospitals and the testing system begins to decline. If you get sick during the period when things are bad, then your prospects are worse. A small amount worse if the system is merely under strain, but much worse if things start to collapse and capacity runs out. Also Paxlovid is coming.
16. 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.

Other modeling observations and general prognosis.

1. Omicron is already the dominant strain. Delta will not go away entirely, but is unlikely to be a substantial presence going forward.
2. Things will peak in January, or perhaps February (or possibly the last few days of December). This is overdetermined.
3. After the peak things will probably decline rapidly, then stabilize at a new normal level. Fluctuations will happen as before, but there won’t be another Omicron peak like this one. If there is sufficient overshoot on immunity things might collapse further.
4. There might be another strain in the future. I don’t know how likely this is, but that’s the most likely way that things ‘don’t mostly end’ after this wave.
5. Once this wave is over and Paxlovid is widely available, restrictions don’t make sense. Continuing to require distancing or masks, or pushing hard on further vaccinations, isn’t justified by the levels of risk we will face, and there’s no collective risk justification either.
6. Taking action to ‘stop the spread’ mostly no longer makes sense. The spread isn’t going to be stopped, that ship has very much sailed. Slowing it down a bit has some value, but ‘pandemic ethics’ no longer apply.
7. Modifying how you live your life also won’t make sense. Covid-19 will be one more disease among many, and life will be marginally worse, but by about April you shouldn’t act substantially differently than if it no longer existed.
8. We’ll have to fight to end many restrictions. They will by default continue long past the point when they stop making any sense. Various forces will fight to use these restrictions to expand their powers permanently.