It wouldn't surprise me if the UK's cases are now dropping because they reached that threshold, but I doubt the US is there now. Probably Delta will blow through literally all the remaining unvaccinated people and that'll be the last surge, at least unless we get a vaccine-resistant strain.

The current dip in the UK is trending toward the former. But it's further complicated by the fact that levels of immunity in the population will continue to oscillate up and down. (Nevermind that once schools open in September, 20% of the population with relatively sparse vaccination will be mixing in large cohorts).

Another factor in herd immunity is vaccine efficacy - which is somewhere between 86% and 95% for the mRNA vaccines (and will continue to change). A herd immunity threshold of 90% presupposes a vaccine with 100% efficacy - when your vaccines are not that effective (not to mention, losing effectiveness over time) it bumps the threshold even higher.

Right now, much of the population has some level of "sterilising immunity" from the first round of vaccines and previous infection (i.e. having enough circulating antibodies to potentially block symptomatic infection and transmission). But everything we know about existing respiratory viruses (and indications so far this year) suggest antibodies will wane.

Of course, indications are most people will come away with robust cell-based immunity. (Those plucky T-cells and B-cells). But eradication for the UK looks *very* close to impossible given the near-total-abandonment of public health measures recently.

Not necessarily the case. Infections with HCoV-229E produces durable immunity and reinfection is due to antigenic drift:

https://www.biorxiv.org/content/10.1101/2020.12.17.423313v1

That it at odds with prior studies that found ~12 month reinfections with coronaviruses, but it is with considerably better methodology.

And it is simultaneously: not clear that vaccines produce sterilizing immunity, not clear it is necessary to do that at all, and not clear if how much measurements of NAbs correlates with sterilizing immunity.

I can tell you a story about how delta reaches 90-100% thresholds of herd immunity in this wave and burns itself out and we don't see it much again for 3-5 years in countries like the US/UK. Or I can tell you a story about how it keeps coming back every year with 2 or 3 waves. Anyone who tells you they know which of those outcomes must be correct probably knows a lot less about virology than they think they do (even if they have a degree). I'm reasonably hopeful its the former, but I never predicted delta and thought we'd be virus-free this summer and was wrong.

Even in the worst case though the vaccinated/recovered are never going back to 2019 levels of susceptibility to severe outcomes, so we're looking at a steady drip-drip-drip of people killing themselves to avoid vaccination up until we get bored with that and they pretty much disappear (that's where T-cells and B-cells and cross reactive partial immunity to all future variants comes in).

We could look at the flu for clues, in that case every year will have one or more variants that are the most prominent.

I'd argue that in the age category with the most infected (10-29 years old) in the UK, that these people are not killing themselves due to their young age.

And the elderly have already gotten the vaccine and are thus up to eight times more likely to not get infected.

By contrast SARS-CoV-2 only has a single chromosome, and so it primarily evolves via "genetic drift". While it's _possible_ for a cell infected by multiple SARS-CoV-2 variants to generate "chimeric" offspring via a process called "crossover" AKA "homologous recombination", that mechanism is much less effective than the simple segment-reassortment that drives flu evolution.

Like the 1918 H1N1 second wave mutation that caused ARDS in 20 year olds?

We still have no idea how that happened, but with this coronavirus evolving to be more transmissible/virulent that is still on the table. If it can evolve to become more transmissible but at the cost of triggering ARDS like that, then it will face evolutionary pressure to do so.

And hospitalization rates of 20-29 year olds aren't anywhere near as good as the fatality rates. While the death rate drops by a factor of 2 every 8 years, the hospitalization rate drops by a factor of 2 every ~15 years. And delta has 2x the hospitalization rate of alpha across age/sex/deprevation/comorbidity matched controls. It should still be about a 1-in-50 chance of hospitalization for 20-29 year olds. There's no proof that number can't continue to get worse.

I don't support the recent abandonment of restrictions, but could that policy, followed up by stricter restrictions in a few months time actually be helpful for eradication? Eradication is likely a hopeless prospect in the UK anyway, because there is no political will for closing the borders. But it's interesting to conjecture.

That's by no means certain; even ignoring the possibility of effective countermeasures, a more transmissible variant could displace it (if we’re lucky, it could also be one producing less severe disease, the way it was when Epsilon variant for a while displaced most others in California, before Delta, which is more transmissible than Epsilon, took hold.)

So if there's overall less replicants of one strain then the other, then the population will effectively select for the more infectious one. Actual geography of course is also key here though: if a carrier flies over to an unexposed area with any strain, it's going to take over if the other one doesn't make it there.

Didn't the UK have another lockdown for this wave too?

Herd-masking seemed like a no-brainer from the beginning. It will be really hard to go back to that in the US after the CDC giving the all clear to go maskless.

...which will happen promptly. The selection pressures are perfect. You already have a variant with vaccine breakthrough, circulating in a partially vaccinated population.

So the question is, is the virus now in a local minima where it is highly adapted for spread (ie big increase in R0 from ‘original’ virus) and are those selective pressures in a situation where the virus can’t jump into a full immunity escape mode without climbing down off mount improbable and taking another face?

My bet would be that the selective pressures may continue to drive fitness for reproduction, but won’t lead to immunity escape because spike is too conserved

The more optimized the covid spike becomes, the harder it is to get better. What frightens me are polymerase mutations.

[0] Darwinian Evolution Can Follow Only Very Few Mutational Paths to Fitter Proteins https://science.sciencemag.org/content/312/5770/111

[1] The rate of compensatory mutation in the DNA bacteriophage phiX174https://pubmed.ncbi.nlm.nih.gov/15911582/

What are these in layman's terms?

This means they replicate quickly, and generate mutagenic variants quickly. HIV and Ebola have this in common.

Delta is already selecting for viral load over vaccine escape - if it keeps getting faster then it could become more dangerous, but it would also increase the rate it can explore it's genetic "phase space".

Or, we're kinda f'd with regular transmissions at the moment, and vaccine escape is a possible accelerant?

Evolution does whatever leads to more of the successful thing existing, so viral loading was a pretty obvious move: the question is whether there's any vaccine-evasion which doesn't compromise that advantageous (Delta suggests yes, but its possible that's as far as it can actually go).

What we do know is that the Spike protein is essential for COVID cellular binding.

We also know that spike has mutated between 'vanilla' COVID of 18 months ago and what all vaccines target, and Delta. This makes sense, because the spike (or S) protein wasn't optimised for binding to Human ACE2 receptors; over time mutations in S (ie with Delta) have lead to increases in binding affinity with ACE2, the result being that Delta is more likely to infect a cell with the same viral load as 'Vanilla'. This would be a perfectly acceptable reason for the uptick in viral loads in Delta and infectivity and hence R0.

We are lucky/the vaccine researchers are smart in that S is quite antigenic (that is, triggers a good immune response, although in a 'natural' infection people will produce antibodies to many parts of the COVID virus), and because the selection pressures driving improvements in ACE2 binding affinity of S have not lead to such a great conformational change that antibody responses are useless (ie antibody-antigen affinity is decreased in Delta, but still effective), our vaccines against the earlier S protein are still effective.

Because of the way evolution generally works, pressures driving S evolution tend to end in a local minima (or maxima, depending on your way of looking at it - i tend to think in terms of conformational entropy so hence Xornot and my use of different terms for the same concept) - or as I mentioned earlier, 'Climbing mount improbable', a term coined by Dawkins in the book of the same name.

It is because it is very hard to get out of these local minima that the human body is full of such oddities, such as an eye that is designed with the nerves in front of the photoreceptors, resulting in a blind spot - it's easier to adapt around the minima to reach a new optimum then it is to reinvent the eye with the nerve in the position that would be logical from a functionality standpoint)

Therefore, it is very very unlikely that the S protein, or the virus, will be able to mutate to a S protein that is so radically different that it escapes antibody-antigen affinity from the vaccines we have today - the S protein would basically have to be completely redesigned, which is really unlikely to occur by the gradual process of evolution. Ie the chances of shaking the RNA coding for S into a new functional protein that works and is a completely new, novel shape, is infinitesimal.

So - basically, total vaccine escape is really really unlikely. Like, number of grains of sand on earth unlikely, if not more so. But polymerase mutations could increase the rate at which the grains of sand are sifted.

It is not something that I personally would lose much sleep over - we don't have any evidence from nature that I am aware of (ie flu virus etc) of highly conserved/selected proteins all of a sudden spitting out a completely new model - basically new diseases that we worry about come from species shifting (ie... let's just say SARS to avoid a debate about COVID origins)

So the important question is: should "we" take the bet on that immunity escape? Or should we not take that chance?

My opinion is that we should act decisively to avoid the bet.... but the UK government clearly feels lucky.

History is mixed here, but most of the mandatory vaccines seem to be extremely effective and to work well for at least decades.

60% (Vaccinated + Previously Infected)

Then you realize that a transmission rate among the timid in ShyFleetersLand and the compulsive in LetsHugLand cannot be the same. Then you realize that that very average number needs explanations of the underlying model to be meaningful - it comes from societal behaviour not just from intrinsic viral properties.

I think you're right, but that will still happen over years in multiple waves. Barring some sudden uptick in people changing their mind about vaccination.

Given the enormous US Covid outbreak, the US is likely not far away. We're at 70% adult vaccination and had a minimum of 100 million prior Covid infections. Also throw in tens of millions of people that likely have natural immunity to Covid.

The biggest question with Delta is going to be the matter of repeat infections and how long the vaccines, the vaccines + prior infections, and prior infections (without vaccination) all hold up against it. To say nothing of what variations will follow next after Delta. Is there actually herd immunity to be found with Delta, or will people just keep getting variations of Covid from here forward. I don't believe there will be herd immunity for any nations, there will just be far lower mortality rates due to prior virus exposure and the vaccines. Some non-trivial % of the vaccinated population will continue to get Covid. If there was a chance to squash Covid with the early strain via herd immunity, those days are very long gone.

The great lie still being persisted for the benefit of the agitated public, is that Covid is going to go away courtesy of vaccinations. The authorities have pitched that to the public from the early days of the vaccines to try to max out the vaccination rates. Do this and Covid goes away. The vaccines are never going to stop Covid, they're going to continue to dramatically reduce the mortality rates (which is critical, however the public still doesn't widely grasp the reality of the forever Covid future yet).

If it becomes century-long endemic in the population, kids are exposed to it, likely creating a productive exposure-related immune reaction until they're old enough to get an mRNA vaccine.

What will be interesting to find out in the near future, is if high vaccination rates + prior infections reduce Covid deaths below, say, 50k people in the US every year, or whether we're forever stuck with a sizable population killer no matter what (short of implementing elaborate forever cultural systems of lockdown; as in, those counter measures will have to become ingrained deeply into the culture, accepted and automatic). The next decade is going to be very weird and interesting on that front.

https://vitamin-d-covid.shotwell.ca/

It may sound callous, but in terms of first priorities, reducing the total number of deaths from COVID19 has never been our #1 priority (to the extent that we've had any clearly formulated priorities at all). The implicit goal, as we were all saying in the spring of 2020, was/is "flatten the curve".

Unfortunately, these two goals, when combined with an infectious agent with a good-sized R0, are really in opposition to each other.

There's certainly an interesting discussion to be had surrounding individual freedoms vs the common good in a pandemic, but I'm not sure as to what extent we can even have those discussions while an embarrassing number of people feel that just being asked to wear a covering over their face in public spaces is an intolerable violation of their personal freedoms. When even the smallest requirements intended to protect the public's health are treated as if they were the harshest forms of oppression imaginable there simply isn't any room left for debate.

Still, for the population that believes a degree of concession can be reasonable and appropriate under such extreme conditions as a global pandemic I think it is possible to strike a good balance between individual freedom and individual and collective responsibility. I think we can work to protect freedoms while also insisting on some measures to help reduce the spread of a virus.

It doesn't have to be an either-or situation at least.

Good guess. As of today, that's the exact number:

https://www.usnews.com/news/health-news/articles/2021-08-02/...

18% of Americans are 15 or younger [1], below the youngest approved vaccine age (the Pfizer vaccine is approved for teenagers as young as 16), so that's (0.18 + (1-0.18) * (1-0.7) = ) ~42% of Americans who haven't even received 1 shot, and 58% who have.

(There may be some error in that, if far more or far less than 70% of non-adult vaccine-eligible people (teenagers aged 16 or 17) have gotten at least one shot, but it probably doesn't change the overall percentage that much.)

[1] https://www.cia.gov/the-world-factbook/field/age-structure

[1] https://www.fda.gov/news-events/press-announcements/coronavi...

https://www.mayoclinic.org/coronavirus-covid-19/vaccine-trac...

...to be quite interesting for covid-19 vaccination information. For example, the state with the lowest rate of at-least-one-dose vaccinations for people 65 and up is West Virginia, at 83.1%. Most states are 90+% or better for that age group.

A very large number of those adults also aren't going to need two doses to reach high levels of protection (against severe outcomes), due to prior infections. One mRNA vaccine dose + prior infection will get you there.

Combined with the recent surge in vaccinations due to Delta concerns, the US will probably see the same drop-off that Britain has by late August - early September.

That is (1) outrageously hyperbolized and (2) completely wrong. Delta wasn't known to have this level of transmissibility until the last three weeks. People, experts, doctors, "authorities", whatever, you want to label them 100% believed sincerely that we were on a path to the elimination of the outbreak.

Cut the bullshit, basically. Yeah, yeah, I know it's HN and everyone wants to think they're smarter than everyone else. But you aren't. You're retconning brand new science to make prior understanding into a "big lie". That's really awful.

Delta was formerly known as the India(n) variant. We've known it had high transmissibility since April or May.

> It would seem to me that by an endemic standard, the Covid outbreak was gone from the US between May and July and has only just recently made a resurgence.

Pffft. Yeah, not even close. At its lowest, the covid death rate was 5x higher than average deaths from influenza over the past decade.

I don't mean for this to be a trick question. 5x the flu is within my comfort zone, but 2x or 1x or even 0.5x could all be reasonable answers. The answer that's not reasonable, but is by far the most common answer I've gotten, is that no Covid deaths are acceptable and we should never stop taking extreme measures to suppress them.

I don't view a statement that puts 100k deaths/year as within your "comfort zone" as a serious attempt to engage, sorry.

That's something to strive for, but extremely different from "elimination"

https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/burd...

If you're referencing the CDC's case study from Provincetown, I think it's important to point out that the R value cited is the R value during Bear Week, not on average.

From wiki: "R0 is not a biological constant for a pathogen as it is also affected by other factors such as environmental conditions and the behaviour of the infected population."

And learned the difference with Rt today (which some others are quoting, eg for Alberta), is that Rt is computed, while R0 is a guess based on a model, to try to normalize Rt so that it is more comparable over time and place. So I thought that was cool!

:) Many of us have felt something along those lines since the early times.

But e.g. the viral load for said variant was reported as _1000x_ Wuhan weeks ago, value changed to _3x_ days ago.

I read the emergence of Tinnitus after COVID-19 weeks ago at _67%_, today at _0.shmbrmbsomething_.

We are flooded in bad numbers. (And of course, that R0 is also circumstantial, vs the examples above...)

COVID-19 herd immunity? It's not going to happen, so what next?

https://theconversation.com/covid-19-herd-immunity-its-not-g...

> we would need to get close to 84% of the global population developing protection against infection (in the absence of non-pharmacological interventions) in as brief a period of time as possible

(...also, there, you find «the reproductive rate [...] is probably closer to six rather than three»)

They estimated that as of June 14, 89.8% of the population would test positive for antibodies.

https://www.ons.gov.uk/peoplepopulationandcommunity/healthan...

Indeed, even with Delta’s terrifying R-value, this seems like enough to suppress the virus.

Some easy-to-grab stats from Canada's worst covid province which is dealing with a Delta wave:

    Alberta provincewide: 1.48 (1.38-1.59)
    Edmonton Zone: 1.37 (1.15-1.61)
    Calgary Zone: 1.50 (1.37-1.64)
    Rest of Alberta: 1.48 (1.26-1.73)

Edit: later learned the parent is talking about R0 and you are talking about Rt, so those numbers are not directly comparable anyways.

In practice, of course, people respond to news about Covid waves and that contributes to the wave-like dynamics. Furthermore, new variants of the virus will be able to reach people that were "cautious enough" for a previous variant. That alone would also give you wave-like dynamics, basically every new variant would affect increasingly harder to reach people.

Anyway, the point is, seeing these waves is super natural and expected and we can't deduce anything about population-level immunity from them without looking really really closely.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4526984/

Sure, _maybe_.

> [...] would seem to indicate that most Western populations are already at herd imnmunity by this point

Given that infections are still rising pretty hard, what indicates to you that we are _at_ this point, and not, say, 6 months out?

That's assuming that nobody who got covid later got vaccinated (or got it before the vaccine kicked in). That seems like a very unrealistic assumption to me. On the other side, there are probably a lot more cases than are reported.

You're right that it almost certainly matters for heard immunity, but i think you need a much more complex model to know how much of an effect it has.

CDC estimated that 1/4 covid infections had an associated positive test. I did the same kind of napkin math you're referring too for Floridia a few months back and they'd could have been at 80% of the population with some level of immunity.

But napkin math probably isn't a good way to run a pandemic response. Just like herd immunity doesn't really matter at an individual level.

https://www.mayoclinic.org/coronavirus-covid-19/map

[0]: https://www.mayoclinic.org/coronavirus-covid-19/vaccine-trac...

Come on, this is silly. We haven't learned nothing over the last year. https://www.nih.gov/news-events/nih-research-matters/lasting...

It's also worth noting that's a study of ~200 people. Given then times we're in it's an excellent sign and possible reason for cautious optimism and I'm sure a larger scale study is much harder to pull off in the midst of the pandemic.

That said, I have yet to see a study on the rate of reinfection of any of the variants against people who had already been infected with the initial strain, and how well that is survived, etc.

I was under the impression viruses became less lethal because if they became more, they'd kill off their hosts and be less likely to spread.

There's a chance you get some super virus that becomes both more transmissible and lethal, but that is very rare (from what I can see).

Only if the lethality is negatively impacting their fitness. If it can spread to another host quickly, who cares if the previous host dies. There's no selective pressure against it.

Which is why Delta is scary. Not just because of the higher viral load, but new strains could be more lethal and still not be selected against.

And let’s not forget about Mareks disease, where a non-sterilizing vaccine is thought to have contributed to a massive increase in virulence, killing nearly 100% of unvaccinated chickens now vs causing mild disease decades ago.

With a different presentation of disease where symptoms and spread occur concurrently then there would be a pressure on the virus selecting for strains that arent so lethal a carrier has no chance to spread. In covid’s case, that pressure doesn’t exist as far as i can see?

There are supposedly over 200 different viruses that can cause the common cold (https://www.nih.gov/news-events/nih-research-matters/underst...). So it's quite possible for immunity to any individual strain to last a very long time and still get multiple colds per year.

> Usually viruses become more transmissible and less lethal in response to rational behavior in their hosts--but humans are proving we're not rational.

Our own "rationality" doesn't matter much, if a virus leaves you bed-ridden or dead, that makes it very hard for you spread it regardless of your choices. The fact that we have so many different viruses which essentially cause more or less the same "common cold" proves that there is very strong evolutionary pressure for a virus to behave this way.

All viruses get less lethal as time goes on, not stronger, despite all the fear porn that has been indoctrinated into the public over the last year and a half.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7252012/

But with C19 we are aggressively isolating people with symptoms. This focuses evolutionary selection pressure on the initial infectious stage. In order to be more infectious the virus increases viral load and shedding, causing more serious symptoms; which would be an evolutionary disadvantage, except isolation renders this disadvantage moot.

Also natural immunity general focuses on the nucleus of the virus, vaccine immunity is to the spike. So this forces mutations in different proteins, which has different results.

This isn't true. Given certain assumptions, it's true on average, but those assumptions don't apply in this case.

For a specific example the Spanish Flu hit harder later on.

Highly-deadly diseases will kill their hosts quickly, limiting their spread. Therefore, one of two things will happen:

• A less-deadly variant will emerge, spread faster, and outcompete its more deadly cousin.

• The deadly disease will kill enough of the population that its R number drops below 1, and thus the deadly disease will die out.

Therefore, observed diseases will tend to get less deadly over time.

---

If you look at the data, we're firmly in “kill enough of the population” town (to the extent you can stretch this model to our situation). The variants we're seeing spread are getting more virulent over time, not less, because:

• we don't want to die and we're doing stuff about that, meaning any model with “most individuals infected are removed from the model” in it is a flawed model; and

• we have fast long-distance travel, so any population model that relies on Euclidean locality is a flawed model.

> Among five COVID-19 patients who were hospitalized, four were fully vaccinated

https://www.cdc.gov/mmwr/volumes/70/wr/mm7031e2.htm

Wrong. It's generally the case, because a virus that keeps its host walking around will tend to infect more people than a virus that sends them straight to the morgue.

SARS-Cov-2 is unusual in that it's asymptomatic infectious period is really quite long. It's straight-to-morgue capabilities could become much more prevalent with hitting its infectivity too badly.

Smallpox.

We've faced strict lockdowns and limited access to vaccines to which makes us a ticking time bomb if we were to let current cases go rampant.

Separately, the physical social graph is not uniform, but complex. There can easily be narrower channels that have a lower probability of conducting infection. Thus, the spread will slow after the easy routes have been exploited.

This argument was made many, many times over the past year and a half by people insisting that <their area has hit herd immunity and everything is fine and we can fully re-open>.

Inevitably, like clockwork, the wave of COVID that would follow would dwarf the previous one.

The only thing that has broken this pattern has been mass vaccinations. It seems that high rate of antibody sero-prevalence in the population only protects you from COVID on paper.

https://www.worldometers.info/coronavirus/usa/north-dakota/

https://www.worldometers.info/coronavirus/usa/south-dakota/

I anecdotally am finding this to be the case

We don't know how much, though. There are cases in which vaccine performs better than a natural infection, there are cases in which the vaccine performs worse than natural infection. Without time for a study, it's impossible to know where we lie with Covid.

https://www.reuters.com/world/uk/new-uk-challenge-trial-stud...

https://www.fox10tv.com/news/coronavirus/getting-covid-19-tw...

https://www.nbclosangeles.com/on-air/one-mans-experience-abo...

https://www.sciencemag.org/news/2020/11/more-people-are-gett...

But how often and what are the consequences.

I have no clue. I hope it works out well.

No, actually; the actual infection sometimes misfires, leaving dud spike proteins outside the cells. If the immune system finds those first, it'll attack the dud spike proteins instead of the still-functional spike proteins, attacking all the viruses that failed to get into the cells instead of all the viruses that might succeed. The mRNA vaccine doesn't produce real, active viruses, so it doesn't have this problem.

> Taking the line of reasoning where we assume the worst case scenario until proven otherwise, would it be reasonable to assume long term medical issues from the vaccinations?

Assuming the worst-case scenario until proven otherwise doesn't work like that. You have to look at the entire range of uncertainty, and choose the worst-case scenario for each question.

Example: you want to know, worst-case, how many people will die from car crashes on a road in a year, so you assume that the cars involved in collisions are travelling at the fastest recorded speeds on that road (or in the 90th percentile of speeds on similar roads, or something). But if you want to know, worst-case, how long it'll take to travel the road, you should assume there'll be loads of traffic jams, or the road will be closed.

So here's a worst-case scenario if people don't get vaccinated, bounded by my amateur knowledge of epidemiology: there's a large enough infected population passing the disease around for a really deadly, fast-spreading variant to emerge, and its antigens are different enough from normal that everyone currently vaccinated is susceptible, hundreds of millions of people die, and COVID becomes a seasonal (but much more deadly) illness, killing hundreds of millions again every few years until it reaches an equilibrium of sorts. (A real epidemiologist would know more, which would probably lead to a less apocalyptic worst-case scenario prediction – but it might lead to an even worse one.)

Here's a worst-case scenario if people do get vaccinated: everyone is vaccinated, COVID-19 starts going away, then a month later, it turns out that the vaccines – and real COVID-19 infections (there's no mechanism in the vaccines that isn't also in SARS-CoV-2, excluding the needle / delivery mechanism) cause some complicated, heretofore-unknown-to-science time-delay mechanism that causes a severe allergy or autoimmune condition. Thousands die before we identify the problem, and tens of thousands die before our politicians get their acts together and authorise the mass distribution of anti-allergy / immunosuppressant medication (which we already have manufacturing plants and distribution networks for). We live with the aftermath, but getting infected would've been just as bad.

This second scenario is a lot less realistic than the global apocalypse one, because I had to pull side effects out of my ass. If the vaccines caused chronic fatigue syndrome, which is the only COVID-19-induced disorder caused by a mechanism that the vaccines could share (because we don't know what causes it), it would've started happening already. But it hasn't. Assuming some arbitrary thing we have a fair bit of evidence against is not how you do worst-case scenarios, and it certainly shouldn't be how you do actual planning.

The second point, your worst case scenario doesn't even address the worst concerns of people who don't want to take the vaccine. They don't trust that spike proteins are the only things in the vaccine. The worst case scenario is not that the vaccine acts like the virus but that it acts different than the virus. And then you get conspiracy stuff like new world order types deliberately introducing things to the vaccine that will make it harder to have kids or stuff. And unfortunately our trusted organizations telling white lies to the public to elicit the behavior they want hasn't helped this trust issue.

But this is all moot for two reasons. First, because someone actually did a study and found that the immune response from infection was ~10 times stronger than from the vaccines[0]. Second, because we've already selected for a virus that is highly contagious and can infect vaccinated people, and will thus continue to be selected to specifically infect vaccinated people since most potential hosts are vaccinated at this point.

In summary, we might have to all be infected, nearly all at once, for this to be over, or just get lucky and the dominant strains will be attenuated to the point where they aren't a major problem.

[0] https://www.biorxiv.org/content/10.1101/2021.07.29.454333v1

Worst-case scenarios should be constrained by your knowledge. I know what's in the Pfizer vaccine, so my worst-case scenarios have to be constrained by that. But sure:

“Worst-case”, somebody's poisoning the vaccines. This leads to severe side-effects from some batches, which the statisticians take entire weeks to notice because they're all asleep on the job. Vaccine roll-out stops pretty-much everywhere, but nobody's able to trace down the saboteur. A dozen new, highly-transmissible and virulent variants emerge, with different antigens to each other and to the vaccines, so vaccinating the populace becomes intractable.

You see that this scenario is incompatible with “everyone gets vaccinated”. The bad stuff largely comes from “people don't get vaccinated”; the only way everyone*'s going to get vaccinated is if the vaccines don't suddenly get poisoned or otherwise become dangerous.

* except the immunocompromised, and others who don't get vaccines for health reasons.

I can't do a “worst-case scenario” where the vaccines are already poisoned, because they're not. It'd be bloody obvious if they were, given how big a sample size the statisticians have to work with. That would be even more blatantly fictional than my “tens of millions die every year” scenario.

Try to understand, they don't trust the government, they don't trust the CDC, they don't trust Pfizer and they don't trust you. Yes you have an official list of ingredients that someone with an appropriate degree can understand. But what's the stuff in the actual needle that you are so intent on making sure gets injected into them? Seems perfectly reasonable to them that some PhDs in some pharma companies are really worried about global warming and a coming Idiocracy. Why not put something in the vaccine that reduces fertility for the unwashed masses?

Maybe it sounds crazy to you and me, but a lot of people hear experts saying seemingly ridiculous things (like needing a vaccine for a disease you already got and recovered from), see how everyone falls in line with the narratives as they come and go, watch mainstream news and social media restrict all alternative points of view. And they don't trust the system. And its clear to them that this system they don't trust, also doesn't like them. From that perspective, of course they don't want the people who lie to them and hate them to have the authority to stick some chemicals and DNA (I know, mRNA) in their arm.

So who're left? The people who are concerned about vaccines because other people are, rather than because of (misplaced in this instance, but not in general) scepticism of the claims of untrustworthy, powerful people. Those people can be reassured by thought experiments, because they're assuming dangers due to incompetence moreso than malice.

¹: I suppose an argument from game theory might, but only if they think the vaccine-poisoning enemy is in it for the long run, so the threat of the truth coming out in (e.g.) 20 years would be enough to dissuade them from something like that. If they think the enemy's plans are shorter-term, or they can afford the loss of face, I don't think there's any way to convince them short of convincing them that the industry behind “non-addictive” heroin, thalidomide (developed by a Nazi war criminal!!) and the contaminated blood scandal is totally cool and in no way out to get you.

It seems to me the worst case scenario is always applied when looking at things like natural immunity from prior infection, long covid, etc

If you model Sars-Cov-2 after Sars-Cov-1 or MERS then you would be lead to believe natural immunity lasts around 5+ years.

Where is worst case scenario not applied? Anything to do with vaccines. We're not even allowed to question it.

We are extremely conservative on one side of the coin, but not the other. Why?

What's the worst case scenario here?

How do you figure that last part?

If we're talking worst-case scenarios from mass vaccination I would think you would need to put Marek's or ADE type outcomes on the table.

Not sure I agree with their ‘hundreds of millions (per year)’ figure. That seems like unnecessary fear-mongering. But maybe ‘hundreds of thousands’ or ‘millions’, which is still not great.

See also: https://xkcd.com/2261/ and https://xkcd.com/883/.

IFR: 0.15 = 613000 * 1 / 0.0015 = 408 million infections (124% population)

IFR: 0.3 = 613000 * 1 / 0.003 = 204 million infections (62% population)

IFR: 0.6 = 613000 * 1 / 0.006 = 102 million infections (31% population)

So in case of the lower IFR would implicate there must be many reinfections. And those reinfections are still deadly. It would imply immunity isn't long-lasting. So best to keep routinely boosting your immunity through vaccines. This would probably be the least favorable scenario.

In the case of the higher IFR would implicate there's still some herd immunity to go. It also implicates infections are more deadly. So better boost herd immunity by getting the vaccine. This would actually be the more favorable scenario if we're going to be able to beat Covid.