>Vaccines that let the hosts survive but do not prevent the spread of the pathogen relax this selection, allowing the evolution of hotter pathogens to occur. This type of vaccine is often called a leaky vaccine. When vaccines prevent transmission, as is the case for nearly all vaccines used in humans, this type of evolution towards increased virulence is blocked. But when vaccines leak, allowing at least some pathogen transmission, they could create the ecological conditions that would allow hot strains to emerge and persist.
It's not just Massachusetts finding that the vaccine doesn't prevent infection. Iceland[2], France, Britain, Germany[2], Australia[3], and Israel[4] are seeing diminished effectiveness of vaccination. The Israeli study in particular is interesting because it divided the vaccinees into two groups of equal size, partitioning by median time since vaccination (146 days), and found that the cohort vaccinated earlier see less protection than those vaccinated more recently. That seems to suggest it's not necessarily the delta variant that's making the difference but time since vaccination.
Looking at Provincetown, it's far from obvious that this is what happened. It seems more likely that a lot of vaccinated people got the virus in close proximity to unvaccinated people, but the chain of transmission mostly stopped there. Numbers in Provincetown have fallen and there were no reports of major outbreaks when vaccinated people returned home. So it would seem like you could have vaccinated-to-unvaccinated spread in some cases, but vaxed-to-vaxed is multiples less likely.
With the large majority of the world still unvaccinated, and most spread (apparently) curtailed between vaccinated individuals, the evolutionary pressure on the virus will still be toward longer incubation and less lethality. Perhaps if we ever reach a point of worldwide herd immunity by vaccination, and still have large scale circulation of the virus among the vaccinated, we'd be looking at a different evolutionary drift. But it's also worth noting that the relevant mutations in Covid-19 are on the spike protein, and there aren't so many configurations, only a few hundred; it's likely that all possible configurations have already been "tried", and are currently competing in the wild.
> Numbers in Provincetown have fallen and there were no reports of major outbreaks when vaccinated people returned home. So it would seem like you could have vaccinated-to-unvaccinated spread in some cases, but vaxed-to-vaxed is multiples less likely.
I think time will show this to be false. A shockingly high number of the vaccinated have actually already had COVID (some of them explicitly knew they had it yet chose to get vaccinated anyway, sometimes at the advice of their doctors, which is horrifying to me insofar as it reveals fundamental ignorance about natural immunity), but of those who haven't been exposed to real SARS-2, a strain capable of readily infecting them will just as easily pass to their vaccinated friend, given the "strategy" of the virus is to acquire point mutations on the S2 subunit that render the vaccines (which protect ONLY against the spike protein) ineffective
> Looking at Provincetown, it's far from obvious that this is what happened. It seems more likely that a lot of vaccinated people got the virus in close proximity to unvaccinated people, but the chain of transmission mostly stopped there.
That doesn't seem to be the case in Gibraltar. There is a ~100% vaccination rate there and an increased number of infections recently.
Gibraltar has an open border with Spain, which is nowhere near fully vaccinated. They've had an uptick (a few hundred cases since April, though almost no deaths). It seems rational to think that most of those cases among the vaccinated were brought there by unvaccinated people from Spain, and are not running wild in vax-to-vax chains of transmission.
The only "news" pieces I could find about Gibraltar having some massive surge were from hardcore antivax websites - the top one was something called welovetrump.
I certainly hope the similarities with Marek's disease reaching 100% mortality begin and end there. What I can personally extrapolate is that allowing or even advising vaccinated people not to wear masks and distancing is rather dangerous.
Masking has never been sufficiently proven to be effective against the spread of respiratory viruses. For SARS-2 specifically we have one randomized controlled trial, DANMASK, which showed no effect of masking (note the primary endpoint was self-infection not community transmission, but self-infection is a decent proxy, and furthermore community transmission is incredibly difficult to study, which is why it is so evil to me that the public health establishment convinced people that "my mask protects you, but not me" when there's actually never been evidence that it protects others as evidenced by the utter lack of studies on that part specifically)
For the pre-2020 studies, they were more or less in agreement that masks didn't help, even in healthcare workers, who tend to be better trained and more compliant with masking protocols. Indeed Macintyre et al provides strong evidence of the risks of cloth mask wearing; while this study compared cloth masking to standard practice, not no-masking, it at a minimum establishes the very real risks of cloth mask wearing: https://pubmed.ncbi.nlm.nih.gov/25903751/
A possibility [1] [2], though contagion is shortened substantially with vaccine, so unlikely still. Probably a good idea to wear masks and physical distance until infections go down.
This virus being novel and widespread, there's nothing to do to stop random mutations. But avoid training it, and get the shots.
I love this kind of stuff intellectually -- deep dives on how edge cases can produce counterintuitive results.
But I'm surprised to see HN uncritically assume this is relevant to Covid [1]. This article deals with viruses that have trouble spreading because they kill the victim too quickly. That's manifestly not the case with Covid, which (when compared to really nasty things like ebola or apparently Marek's) kills a relatively low share of its victims and isn't particularly quick about it.
[1] Or at least the top two top-level comments do as I'm writing this.
> Conventional wisdom is that natural selection will remove highly lethal pathogens if host death greatly reduces transmission. Vaccines that keep hosts alive but still allow transmission could thus allow very virulent strains to circulate in a population.
Host death does not stop transmission of Covid-19 so I do not think this study is particularly relevant, if we’re reading it in that context.
I agree. To my understanding, it's basically the polar opposite -- it's primarily spread by walking, healthy-ish people in the early stages of disease.
In the case of Delta it almost certainly didn't. But the fact that something happened through one mechanism doesn't mean that it can't happen through another mechanism.
I touched on this a bit in another comment but there's more factors than lethality at play. If a virus makes you sufficiently symptomatic you're much more likely to isolate. Conversely if it remains completely asymptomatic you will spread very little. So they're targeting a sweet spot of symptomaticity. You can very easily imagine a strain that would lead to the sweet spot of symptomaticity in a vaccinated person, which therefore would tend to "overshoot" and be excessively pathogenic in an equivalent unvaccinated individual.
In fact, this is a bit of a tangent, but I suspect part of the reason the vaccinated are spreading Delta so much, is that it causes normal cold symptoms in them (which btw the original SARS-2 did too despite how people would act like it's way different); and imo because the media and the "expert" class has so sufficiently scared them that SARS-2 is this scary supervirus, they assume their run-of-the-mill cold symptoms can't be COVID and keep engaging in society without getting tested or anything *
As very circumstantial evidence of the above hypothesis, I would point to https://www.nejm.org/doi/full/10.1056/NEJMc2009787. This was before vaccination but it's a case report of people who actually had SARS-2 (if we can trust PCR; given the symptoms I think in this case they really did have it), and indeed had COVID (+ pre-existing risk factors) bad enough that they ended up developing strokes. And yet even though these were actual covid patients who eventually developed strokes:
> "Social distancing, isolation, and reluctance to present to the hospital may contribute to poor outcomes. Two patients in our series delayed calling an ambulance because they were concerned about going to a hospital during the pandemic."
So my interpretation of the above (this is me reading between the lines) is that even though they felt like shit, they thought actual COVID was even worse than that and thus avoided going to the hospital so they wouldn't catch COVID, not knowing that they already had it...
* Note I don't necessarily think this (unintentional spread) is even a bad thing, I am firmly on the side of "SARS-CoV-2 will propagate through the population no matter what we do and the more we flail about and needlessly damage ourselves the worse it will be". But from the perspective of the average vaccinated person, they are probably very against the concept of spreading it and thus if they were aware that their "cold" was really SARS-2 they'd act way differently
It is not very difficult to imagine that antivaxxers would use this article as proof that vaccination was a mistake and that we should not go further. However, this bit:
> Our data show that anti-disease vaccines that do not prevent transmission can create conditions that promote the emergence of pathogen strains that cause more severe disease in unvaccinated hosts.
Actually makes a convincing case for anyone who did not get the vaccine to get it.
Anyway, that won't convince hardcore antivaxxers, so we shall see in the upcoming months/years whether this article actually transposes to our situation. Just a shame this may be happening at the expense of gullible yet still good at heart people.
Interestingly, antivaxxers have been told their actions put others at risk, but they believe personal liberties are more important.
If that sentence you quoted comes to pass and a vaccine protects those who receive it, yet makes the disease more dangerous for everyone else, it will be the exact opposite situation. How many antivaxxers will cling to their ideals of personal liberties when they are on the losing end of the situation?
Of course, it works the opposite, how many have thought it irresponsible of antivaxxers to put others at risk, but then would ourselves put others at risk with such a vaccine?
Human interactions are interesting and complicated.
Yep. For the record I will literally die on this hill - if from COVID-19, or whatever variant, so be it. Freedom is much more important than safety right now.
The rub is that there are a lot of people on Earth. And, early evidence _might_ suggest that the vaccines that are available lose effectiveness sooner than originally thought. For example, [1] shows evidence of diminished effectiveness after 146 days.
Back to "Our data show that anti-disease vaccines that do not prevent transmission can create conditions that promote the emergence of pathogen strains that cause more severe disease in unvaccinated hosts." and whether that implies that "for anyone who did not get the vaccine to get it." This sounds like a strategy that hinges on everyone on Earth getting vaccines and frequent-enough booster shots. What if that's unachievable though? The logistics for that would be unprecedented. What are the consequences of trying but failing to do it?
> lose effectiveness sooner than originally thought
To be precise, have partially reduced effectiveness against transmission of a variant of the virus evolved after the creation of the vaccine, while still preventing almost all severe illness/death.
Possible ways forward: (1) give people additional booster shots of the existing vaccine; (2) develop a modified vaccine booster targeted more precisely to the variant virus; (3) keep public health measures in place (e.g. requiring everyone to wear face masks indoors) so long as Re > 1.
> What if that's unachievable though?
It has been more or less achievable for past vaccinations. It is a logistical challenge to be sure, but modern society is certainly capable of it if it is prioritized.
"Can create conditions" in the sense that any actions that perturbs a system can have that effect.
With, for example, antibiotics, resitance is quickly lost in their absence. Why? Because it's a costly adaptation to a need that no longer exists.
By the same mechanism, adaptation to the vaccine–if it happens–will by definition tend to be net-negative for the virus' fitness in unvaccinated people. Otherwise, that adaption would also happen without the virus.
All that's entirely theoretical, of course. Because the vaccine, despite the breakthoughs, still prevents the vast majority of infections. And that effect swamps everything, including hypothetical Quergedankenexperimente.
But, of course, they'll run with it, seeing how it's eaten up here as well. Personally, I'm no longer losing sleep over it since everyone I care about has been vaccinated, and most of my future attempts to explain evolutionary biology will be on the theme of "Darwin Awards".
The science has already changed on this just last week. the CDC now recommends vaccinated wear masks indoors again because vaccinated are transmitting the disease and “have the same viral load” as non vaccinated. I try to avoid Reddit comments as a reference because they are nothing but mob consensus and even less accountable than news articles which have an obligation to correct if found wrong. Here is a Washington post article that tells us that at least with these vaccines that vaccinated are spreading the virus. Again this is completely new recent data on Delta only, which the vaccines weren’t made for, so it’s natural actually. While, vaccines do offer protection they aren’t stopping the viral load and aren’t stopping transmission of delta. https://www.washingtonpost.com/health/2021/07/29/cdc-mask-gu...
Point taken. Askscience top comments do tend to be self correcting, usually a back and forth if something is off. It’s not the be all of information gathering indeed.
In any case, we aren’t done yet when it comes down to it, if the numbers are correct.
Those responses mean that you still do get new variants without a vaccinated population. But this doesn't tell me anything about the effect of moderate partial vaccination. It might or might not be problematic but you can't infer that from what happens when there's no vaccination. In other words, "we know that A causes B, therefore C doesn't cause B" isn't valid reasoning.
Simply said, inferring from those answers, the longer a virus is in a host, the more dice rolls. So the worse a partial vaccine works, the more dice rolls, but less for someone not vaccinated. On Delta, numbers are still coming in afaik (I did read something in the range of 36-high eighties for a breakthrough case in another article today, but again more data is needed)
A subreddit that's full of [deleted] isn't trustworthy. Unlike HN, non-admins can downvote posts they don't agree with on Reddit. A subreddit full of [deleted] indicates it's one sided.
I’m not sure about askscience but the “science” Subreddit is completely partisan and non ruled. And the science is still changing, delta is brand new. These vaccines weren’t made for Delta at all and aren’t stopping transmission, however they do offer protection from symptomatic disease, per the CDCs own documents and new recommendation that vaccinated wear masks indoors. Per this Washington post aritcle 75 percent of new cases in highly vaccinated Singapore are in already vaccinated people, similar to the unpublished CdC internal data which made the CDC revise their mask recommendation. https://www.washingtonpost.com/health/2021/07/29/cdc-mask-gu...
Your understanding is 100% correct. Moreover, last I read about it, covid's peak viral shedding was in the pre-symptomatic or early symptomatic stage -- it's most infectious in walking, healthy-ish people.
(The submitted paper is about "highly lethal pathogens" where
"host death greatly reduces transmission". That's the opening line of the abstract, and I'm baffled how anyone would link this to covid).
(edit: first version had a horrific typo, /s/incorrect/correct/)
>“We do not have conclusive proof. But more and more studies and real-world evidence points to fully vaccinated people, who are not immunocompromised, are less likely to transmit the virus if they become infected,”
I've edited my comment (there was a horrific typo) -- I 100% agree with you. Covid is *not* disease like Ebola, whose transmission is self-limiting by its lethality -- it's the opposite.
It's not as simple as lethality. Generally a pathogen needs to cause some sort of symptom in the host to spread well, but the more severe the symptoms the more aggressively the person would isolate. Insofar as the vaccines mostly worked upon their initial release, you can imagine a new strain that is much more virulent (replicates significantly faster, etc); such a strain could cause a vaccinated individual who would normally be completely asymptomatic and therefore not infectious [hopefully we all accept by now that there is pre-symptomatic spread but not asymptomatic spread, if not you're behind a year on the research], to become symptomatic and therefore capable of transmitting. If that same strain were to infected an unvaccinated individual who had never been exposed to the real virus, it might cause much more severe symptoms in them.
---
There's also the separate phenomenom of immune escape. The current major vaccines (mRNA and adenovirus-vector) all just make the body's own cells express (generate) the spike protein (S2 subunit), and nothing else. So specifically point mutations in the S2 subunit could allow some degree of artificial immunity evasion (it wouldn't work against those naturally infected because they were infected with whole, live-replicating virus and thus have much more diverse epitopes for their immune system to "learn" and possibly a stronger immune stimulus in the first place)
Yep. Spoke with someone who worked on the Moderna vaccine about this.
The short of it is, the window in which the virus can / has an opportunity to mutate is shortened by the vaccine. Thus, vaccinated individuals may be host to mutations if they catch COVID but given fewer “dice rolls” - if you want to call it that - would be similarly less likely to create an especially worse mutation.
Couple that with the reduction of spread given by vaccines, and the difference is staggering.
This paper is being wildly misinterpreted and cherry-picked by people who aren’t involved in the science, or qualified to consume it.
Is it possible that it gets fewer dice rolls but the "dice are loaded" by the fact that a vaccinated but contagious case is likelier to spread only selected mutations? Isn't that the concept of immune escape[1]?
Exactly this. Insofar as the vaccines actually worked to protect people who had never acquired SARS-2, an even somewhat vaccine-evading mutation has a sizeable population of real-SARS-2-naive individuals to spread through (i.e. the vaccinated who never had natural infection).
This is why I and others have opposed the concept of mass vaccination for an endemic highly-spreading respiratory virus. It simply doesn't make sense unless you can develop a vaccine comparable to natural immunity (both in magnitude of immune response but also robustness/resiliency to mutations; over the long-term the current vaccines offer neither).
SARS-2's risk is incredibly well bounded; we have a great idea of who is truly vulnerable and who would have to get struck by lightning 8 times in a row to be seriously harmed. We should have recognized that fact from the beginning; but recognizing that fact runs counter to the narrative required to scare the whole population enough to accept lockdowns/etc.
I mean, I agree. I have serious concerns about the potential for over-sensitizing the adaptive immune system, even with the current vaccines. I also fundamentally disagree with vaccinating just against the spike protein rather than the whole virus (particularly given how immunogenic and therefore pathogenic the spike is; we're injecting [genetic material that codes for] the most dangerous part of the virus with these vaccines IMO)
I'm just pointing out how effective the vaccines would have to be for this strategy to make sense (and that's ignoring the whole matter of people that refuse to get vaccinated against COVID, like me).
Simply put the whole strategy doesn't make sense on utilitarian grounds. I don't need to invoke any libertarian principles to argue against why this is so insane.
Side tangent: Unfortunately many who are on my side of the fence as far as skepticism of mass vaccination, believe equally absurd things like the notion that we can eradicate SARS-2 by having the whole world all take ivermectin at the same time. This idea was non-ironically advocated for by Bret Weinstein...
I’m a bit concerned as to what it really says that this is front over material on hn.
The short of it, is suspect a substantial sub population here are holding a variety of opinions that ultimately result in vaccine reluctantance. While the numbers aren’t so fast as to be significant to public health, I do think it forms a sort of idea laundering or affirmation by social proof. In other words people are using the reputation of hacker news for having smart people to launder and promote anti vax.
Interesting you're so focused on the "vaccine hesistancy" side of the fence. Do you have any concerns about people using their prestigious degrees and credentials to frighten the population completely out of proportion with their actual risk from a pathogen, in order to persuade them to comply with top-down public health measures?
It sounds a lot like you just don't like the conclusion that this classic paper leads to: that the "societal benefit" of mass vaccination with an imperfect vaccine is not nearly as clear-cut as many have been led to believe.
My advice to people is to treat the vaccines as a personal risk reduction tool and little else. The only way to actually guarantee you won't infect someone you interact with, is to have acquired (and recovered from) the natural SARS-2 virus, which will build robust immunity. As far as immunity to reinfection, looking at antibodies alone, IgG levels stay seropositive for ~3.5 years:
> Based on these half-life data, we estimate that the median times for IgM, IgA and IgG to become seronegative are 4.59 (IQR 4.12-5.03), 7.78 (IQR 6.71-9.16) and 42.72 (IQR 33.75-47.96) months post disease onset.
> This study suggests that SARS-CoV-2 infection induces robust neutralizing and binding antibody responses in patients and that humoral immunity against SARS-CoV-2 acquired by infection may persist for a relatively long time.
and furthermore once those IgG levels fade you will still have immunological memory, which lasts basically forever and allows your system to much more rapidly and effectively respond to future infection, leading you to have a much lower peak viral load, lessened symptoms (usually fully asymptomatic) and therefore a near inability to transmit the virus.
There’s no way for public to make vaccination decisions on their own. They just don’t have the knowledge and the skills to interpret the data. I mean, it’d be silly if we said: “Hey, you’ve got colon cancer? You could do chemo or surgery. Your pick!”. And unlike cancer, pandemic has impact not only on your health, but on others too.
This is a really sad reality. The internet has empowered us as a civilization but also emboldened a lot of folks who haven’t the expertise to digest immunology research.
Joe Rogan and an afternoon on Google Scholar isn’t a replacement for a couple decades of immunology work.
Whatever we do, if we do not do it decisively, we just give the virus occasion to adapt.
population of hosts * selection pressure * number of generations * ability to pass material to next generation = adaptation
This is the same reason that the optimal strategy to use antibiotics is to avoid using them but when you need to, use a lot of it to make sure you kill completely whatever bacteria it is supposed to kill.
By not vaccinating thoroughly and keeping regime until the virus is largely gone we are giving it right conditions to keep adapting.
We are not going to get rid of this pandemic until everybody gets vaccinated or gets sick.
"Andrew F. Read ,Susan J. Baigent,Claire Powers,Lydia B. Kgosana,Luke Blackwell,Lorraine P. Smith,David A. Kennedy,Stephen W. Walkden-Brown,Venugopal K. Nair"
These are the names of the 9 highly respect researchers who authored the paper. This a post non editorialized and as factual as it can be.
I know this is making the rounds of the 'covid vaccine bad'[0] crowd, but isn't it the case that the yearly flu vaccine doesn't guarantee immunity? How has such a vaccine been flying by with such a potential danger present?
I don't believe it's a matter of 100% guarantee of immunity. The current covid vaccines are designed to prevent severe infection, NOT prevent infection. My understanding is that the current vaccines ~95% efficacy is against severe infection, but we don't actually know what the efficacy against infection is.
For those decrying the fact that this study is about a highly deadly virus, note that mathematically speaking, the same effect would be expected to be observed for a much less obviously lethal virus, if the effect were occurring across billions of hosts, such as what we're currently pushing for globally with the mass COVID vaccination campaign
I have been assuming the idea of these vaccines was to buy time until a new one gets developed that also stops transmission. Ie, I assume we will all get a second vaccine one day that’s better that can have a shot at wiping Covid out, if we get really lucky and everyone takes it
The likelihood of wiping out (as in, totally eradicating) a respiratory infection seems really low. Are there any examples of that happening in the past?
Very relevant when coupled with the Massachusetts study that showed that the vaccinated can still spread Delta with apparently very little problem. https://www.cdc.gov/mmwr/volumes/70/wr/mm7031e2.htm?s_cid=mm...