[mlyle]

Sure.

Even a partial response from a vaccine suppresses the virus and (usually) reduces the risk of transmission. At the same time, it creates a window where the virus is under selective pressure to escape some of the immune response from the vaccine's effects. Individuals who have smaller/partial responses to the vaccine are more likely to have this happen.

That is all I'm saying, and I don't think it's really that controversial. I'm not trying to make a robust immunological argument. I don't think it's inevitable, but it's another reason to reduce transmission. We already have the UK variant, which many have suggested is better at immune escape due to perhaps evolving during a long infection in an immunocompromised individual.

[sudosysgen]

Selective responses against the vaccine are only selected for if those pressures persist during replication. It's not enough to have that pressure at the very beginning, it needs to persist all the way. This isn't really the case for a vaccine.

In other words, by the time the virus is replicating inside of you, it doesn't really have much pressure to evolve to evade those other facets of vaccine immunity, because doing so would probably hurt it.

The UK variant isn't better at evading the immune system from what we know. It's simply more infectious in general.

[mlyle]

> Selective responses against the vaccine are only selected for if those pressures persist during replication. It's not enough to have that pressure at the very beginning, it needs to persist all the way. This isn't really the case for a vaccine.

I disagree. You have the weak vaccine response the entire duration of infection applying selective pressure. What you say seems to disagree with the consensus of the literature, e.g.

https://www.medrxiv.org/content/10.1101/2020.11.17.20233726v...

> The UK variant isn't better at evading the immune system from what we know. It's simply more infectious in general.

The mutations have been broadly described as "immune escape mutations" and are thought to have emerged from pressure to escape low numbers of existing sterilizing antibodies within the host, e.g.

"The unusually high number of spike protein mutations, other genomic properties of the variant, and the high sequencing coverage in the UK suggest that the variant has not emerged through gradual accumulation of mutations in the UK. It is also unlikely that the variant could have arisen through selection pressure from ongoing vaccination programmes as the observed increase does not match the timing of such activities. One possible explanation for the emergence of the variant is prolonged SARS-CoV-2 infection in a single patient, potentially with reduced immunocompetence, similar to what has previously been described [17,18]. Such prolonged infection can lead to accumulation of immune escape mutations at an elevated rate"

https://www.ecdc.europa.eu/sites/default/files/documents/SAR...

[sudosysgen]

The article you linked first assumes only one or two antibodies.

As I said before, there is some pressure for antibodies, but the immune system is way more than that, and people can clear infections very effectively without any antibodies at all.

As for your other link, it's important to know that this a preliminary article that, on those subjects, gives ideas without data. Further research has shown that this variant does not seem to increase disease severity, and instead is just more infectious, as the spike protein evolved for higher binding affinity.

[mlyle]

> The article you linked first assumes only one or two antibodies.

Assumes only a couple of neutralizing antibodies, which is fair for the vaccine candidates-- immune assays of Moderna's vaccine show two typical antibody binding sites against the RBD that are strongly neutralizing. I haven't seen the ELISA data for Pfizer's vaccine.

Given that we've got several papers describing how immune escape variants of other viruses have emerged in the past... I'm curious why you don't think it's much of a risk here?

e.g. https://pubmed.ncbi.nlm.nih.gov/11410701/

> As I said before, there is some pressure for antibodies, but the immune system is way more than that, and people can clear infections very effectively without any antibodies at all.

Of course. I'm not speculating that there's going to be some nasty variant that completely eludes our immune response. I'm saying that it is likely-- and the consensus opinion-- that there is a real risk that the virus mutates to render the vaccine less effective.

> Further research has shown that this variant does not seem to increase disease severity, and instead is just more infectious, as the spike protein evolved for higher binding affinity.

Some of the mutations slightly increase binding affinity. Other deletions look like their primary fitness advantage is immune escape. A missing stop-codon also increases mutation rates for a portion of the RBD, which implies we can expect quicker emergence of subvariants.

It's like you're having an argument I never was having: I have never said that this is likely to cause more severe disease. I am just saying that the virus will be under selective pressure to evade the vaccine-induced immune responses-- which is something I think everyone agrees. This is less likely to happen if there's less infection around and people get vaccinated quicker.

Even in the worst case, where such a variant evolves quickly-- I don't think we're that bad off. As you mention, there's other immune responses. Strong T cell mediated immunity will almost certainly be cross-reactive and strongly reduce the risk of severe illness. We'll have more time to adjust vaccines without mortality accruing as quickly. It is still something we'd prefer to avoid at all costs.

[sudosysgen]

The point of the argument here, from my point of view, is this. In the one to three months between full vaccination of vulnerable individuals and drastically reduced R due to general vaccination, is a variant of the virus going to appear that will be able to effectively infect vaccinated people and spread enough for the pandemic to continue?

The answer to this is very probably no. There is a huge difference between the virus making the vaccine less effective eventually, the virus making the vaccine less effective within one to three months, and the virus making the vaccine sufficiently less effective that it can sustain an epidemic among vaccinated individuals. The second is not very likely at all, because for it to happen a variant of the virus would have to mutate, and outcompete the dominant variant, that has a spike protein sufficiently different that it can keep R>1 among vaccinated individuals.

For this, the virus would not only have to evade antibody response sufficiently for there to not be sterilizing immunity, but it would have to do evade the much swifter and effective non-serological immune response enough to stay infectious.

All of this would have to happen in a subset of the population that has a 20x lower chance of being infected and even when that happens, the infection would be much shorter with most of it with completely different evolutionary pressures.

In one to three months.

It would also have to compete effectively against other variants in the non-vaccinated population while it is doing so, because non-vaccinated people are by very far the dominant infection vector. So it would have to evolve this not only in vaccinated, but also non-vaccinated patients, unless you believe that these extensive mutations will happen in one, vaccinated, patient, which is pretty much impossible.

[mlyle]

> The point of the argument here, from my point of view, is this. In the one to three months between full vaccination of vulnerable individuals and drastically reduced R due to general vaccination,

Not a given. It's very likely, but we don't know how effective the vaccines will be in preventing transmission. Certainly there is past precedent for the opposite.

Also, there's likely to be pockets of population with poor vaccine penetration, so even if it confers sterilizing protection, we're likely to see endemic spread in these subpopulations continually challenging the vaccinated population.

> is a variant of the virus going to appear that will be able to effectively infect vaccinated people and spread enough for the pandemic to continue?

We see a hepatitis B vaccine escape variant every year or two, despite a much lower community disease burden. I don't think anyone can know how likely this is.

> All of this would have to happen in a subset of the population that has a 20x lower chance of being infected and even when that happens,

It's not very likely that the population has a 20x lower chance of being infected; the vaccine almost certainly does more to prevent symptomatic illness than any infection. They've shown a 20x lower chance of symptomatic illness. You're also leaving out the critical window before the first dose where protection (against symptomatic illness) slowly climbs over weeks to 70-80%.

> It would also have to compete effectively against other variants in the non-vaccinated population while it is doing so

Already the currently circulating variants are not equally neutralized by the vaccine. There's going to be immediate pressure making the variants that are least impeded more prevalent.

> unless you believe that these extensive mutations will happen in one, vaccinated, patient, which is pretty much impossible.

Again, the most likely scenario for the emergence for the UK variant is prolonged infection in one person with a low immune response. People like this are well represented in the groups we're immunizing first, too.

These things aren't mutually exclusive, though: you start off by favoring the current variants that the vaccine is least effective against. Then, you have ongoing evolution in vaccinated individuals with lower responses. Then the favored variants become endemic, circulating mostly in subpopulations with lower vaccine coverage and occasionally finding vaccinated people who are more susceptible.

How quickly it all happens depends upon total disease burden. I agree we will probably not get a worst-case escape variant in the first few months of the vaccination campaign, but I think we'll probably see some adaptation towards escape and lowered efficacy. Indeed, you don't even need mutation for that: just preferential selection for existing variants with lower vaccine efficacy.

No one's done the assays on the UK variant yet, but I will not be surprised if the current vaccines are somewhat less effective against it.

If the disease remains endemic with relatively high levels of circulation, variants that escape the current vaccines will be all but certain in the long term.