AstraZeneca Scientist Says Delta Variant Makes Herd Immunity Impossible

if the problem is that the immune response drops too low to prevent infection then there may be no herd immunity from that either, it can just cycle around.

With highly contagious diseases, herd immunity is kind of a meaningless concept. Eventually close to 100% of people get infected.

The measured viral load is substantially higher (e.g., 1000x in some studies) vs the original strain, and it is suspected, but not proven (afaik) that this translates to more exhaled virus.

What is known is that the virus ramps up in the infected people more quickly, and stays infectious longer, so for sure, each person is infectious for more days on both sides, increasing infectious opportunities.

In the vaccinated population with breakthru Delta cases, the viral load initially approaches the load of unvaxed people in the first few days after becoming detectable, but then falls off much more rapidly.

I read this article, it sheds some light on this:

https://www.pbs.org/newshour/health/how-these-mutations-made...

Isn’t that partially because some people had better resistance to it and the survivors passed it on? https://www.studyfinds.org/bubonic-plague-human-immunity/

Is this a trap question? I mean you can make 2 cases.

Firstly the noncontroversial part: covid is a virus, bubonic plague is a bacterium. In the covid case, infected people infect others. Stay away from people, especially in restaurants (so, probably, eating near an infected person is a strong vector), and there isn't much chance of infection. In the case of bubonic plague: enter a building where an infected person had a shit 2 months before ... there's a decent chance you get infected. It's a world of difference. Objects are safe, with covid. Streets are safe. Beds are safe. Public toilets are safe. Public toilets would be a death trap with the bubonic plague.

You ignore age? They're comparable in death rate.

You only count people under 40 (life expectancy, without bubonic plague, was only about 30-40 years when bubonic plague got it's big moment). So if you compare that to what covid does to people <40, it's much less than the mildest flu ...

Let's say you relax that by a lot and say, no people live to 70 in the 14th century, about double the real figure ... covid is about an average flu.

So ... like everything, it depends. If you make a case based on years lost, covid is an exceptionally deadly flu, but less than 1% as bad as the bubonic plague.

If you make a better comparison, and compare Covid to Tuberculosis, today, then for the first 4 months it got to about half as bad as TBC, then fell off a cliff. If you take an average over a year, TBC wins on all fronts: people infected, people killed, years of life destroyed, ... well, except on dollars spent.

BUT covid kills many rich old people in the west. Tuberculosis kills young poor adults, mostly in the third world. Tuberculosis produces orphans. Not that I don't think rich people in the west they have right to a few more years, they very much do. But you want to help humanity, it's the wrong target.

So Covid only really wins from even contemporary diseases in the "dollars resisting the deaths" department.

It’s not a US issue. The delta variant did not originate from the US. If we want to fix this we have to help other countries.

You could also make the argument that letting the initial variant of the virus run its course may have been wiser than society wide mandates that prolonged it. Given the low infection fatality rate, if everyone under 50 in the US caught it, we would have around 30,000 deaths (or same order of magnitude if my estimate is off) because the IFR for those under 50 is so incredibly low. Then the rest of society would be well protected as well and we would have a high natural immunity against new variants that developed. If enacted worldwide, perhaps the reduced transmission may have avoided the delta surge altogether. Note that the CDC’s projections show that a higher natural immunity would mean reducing cases for delta even with limited masking.

Also the first SARS was far less transmissible. Generally speaking as viruses mutate, they tradeoff R0 and severity. It is unlikely the first SARS would have evolved a variant that was more transmissible and equally fatal.

EDIT: Note that even though increased transmissions can mean more mutations leading to dangerous variants anyways, if the alpha variant were spreading broadly before something like delta was broadly spreading, then the delta variant would contend with a higher natural immunity in the global population, which would make it difficult for delta to take hold in the same way. The CDC’s own presentations show that even a limited increased natural immunity of 35% would mean that delta cases would reduce without new masking mandates or restrictions.

It's really not about politics, the vaccine simply didn't roll out fast enough to the entire population of the planet. What happened in the US is actually not that relevant as the US is only about 5% of the population of the planet, i.e. it's only 5% responsible for mutations, as the rate of mutations is proportional to the size of the susceptible population.

This is actually a "shortcoming" of tech. In quotes because the tech of the mRNA vaccines is actually stunning, but it just wasn't fast enough to test and manufacture (development was pretty much instant, the vaccines were ready in January 2020).

Delta’s rapid evolution and plausible defeat of the vaccine which was rolled out incredibly fast, on the back of unprecedented economic lockdowns implies to me we didn’t stand a chance absent a global totalitarian regime just imprisoning everyone in their homes for a year by force.

“ We had a chance to keep a new disease under control, but it's increasingly looking like humanity blew that chance.”

???

The article says vaccinated people spread the virus; if everyone wore N95s, wildlife could still be spreading COVID so it would come back once masks were off… (unless we discover a delta vaccine that we roll out to the world over the next N years while everyone isolates and that prevents vaccinated people from spreading)

just a consequence of globalization, even 20 years ago the world was much less connected and things didn't spread as fast. Doesn't help that the entire planet wasted at least a month trying to contain it when rumors of something emerged in at least December 2019. Corona was being downplayed until basically the 1st week of March 2020

seems like Covid is going to be endemic like the regular flu where each year they have to try and guess which strain to make vaccines for

Any chance to keep the disease under control was lost the moment a carrier got on an international flight on Wuhan. After that uncontrolled worldwide spread was inevitable. Those who think containment was possible are engaging in magical thinking and fail to understand the mathematics of exponential spread.

Even if in the US we had achieved 100% immunization for the covered ages, there are parts of the world which are way behind and it would have happened there if not India, Brazil or the UK.

So it's a false proposition to say if we in the US had achieved 100% immunization it would have stopped any mutations. It would not have.

> We had a chance to keep a new disease under control, but it's increasingly looking like humanity blew that chance.

Vaccinating 8.5 billions of people in a very amount of time is clearly not a reasonable goal to begin with. Even without war, extreme poverty, lack of access and political chicaneries about the who and what.

Humanity's best minds have been trying for years to create a vaccine for coronaviruses that last without success. Now we've tried to do this in less than a year and we don't know the long term effects, therapeutic or otherwise; and if someone does please provide your time traveling machine to the nearest university at once.

So yeah, the virus will become endemic, variants will appear constantly. What we do now is not a decision the people in white coat or black robes can or should answer.

I think this is where people are reminded that Delta started in India, not the USA.

Like pfizer delaying the vaccine after the election ?

They don’t stop transmission but reduce its likelihood significantly. It seems someone who is vaccinated and very ill can be very infectious but generally vaccinated people are unlikely to infect others (reduced observed R0).

Vaccines definitely reduce transmission, just to a slightly smaller extent for the Delta variant. The CDC's messaging on this issue has been atrociously bad.

The vaccines don't stop transmission, but they still radically reduce it. Pfizer is 94% effective [1] in reducing transmissions of the original strain. Even with the delta variant it is still 64% effective:

[1] https://www.businessinsider.com.au/israel-may-reimpose-coron...

The do vastly lower the rate of transmission. That could translate into lower peak hospital utilization (even not accounting for their ability to prevent illness) which is good for everyone.

I do agree that this thing is going to spread in an unbounded manner regardless of what we do now though.

Total guess: Slows down transmission. Those that are asymptomatic should have a lower viral load, which results in fewer cases.

You may be misremembering the initial releases from last November. The goal of the first round of studies was to establish whether the vaccines were effective in protecting people who received the vaccine. The studies were not designed to determine whether it still spread, and so the statements were very precisely worded as "has not been verified to prevent transmission", or things to that effect.

Unfortunately, the English language doesn't make any distinction between "has not been observed" because it hadn't been studied yet, and "has not been observed" because it doesn't exist. Later studies have determined that vaccination greatly decreased the transmission, but by then the idea that they only protect the individual had taken root.

Yes, the vaccines are still very effective against severe disease. It is transmissibility that's changed dramatically.

That is exactly what the article says (25x less likely to have a severe case/die).

The point is the transmissability (as also recently published by the CDC). You yourself get a milder case if you're vaccinated and catch Delta. But you can now still transmit it to children that can't be vaccinated (and who potentially are in a risk group), friends that have a contra-indication to vaccination but are in a risk group etc.

Many of the vaccines are effective against the delta, but they do not serve as a firewall to stop the spread of infection within a community.

As a simple example, imagine you have a community of 100 people. 1 person is infected, 98 are vaccinated, and 1 is uninfected and not vaccinated.

Ideally the 98 people who are vaccinated don’t contract the virus, and do not serve as vectors of spread for that one unvaccinated person. In essence, you make it so the one infected person has to come in contact with the unvaccinated person.

With delta, the 98 vaccinated people are astronomically less likely to die or become severely ill from covid; however, they still can contract and pass along the virus… Which can eventually make its way to the one unvaccinated person at the end of the chain.

So, vaccines are great. Vaccines work. These vaccines are awesome for how fast they were produced. But they aren’t able to serve as barriers of protection for the unvaccinated in a way other vaccines for other diseases.

We have 45% of Americans refusing to get a vaccine now, imagine the push back if we are attempting to get people to take a new one every 6 months. I don't have a better answer I just know that absolute chaos is down that road.

I can’t read the article because of the pay wall. But the claims I’ve seen elsewhere basically say even with a perfect vaccine, you’d need something like 90% coverage to try and snuff out delta with vaccines alone because it is so incredibly contagious. So to a certain extent you can’t just fix the problem with a new vaccine.

> but are those mutations antithetical in some way to antibody production?

The problem Delta presents to antibody-based protection is that there is a several day lag in the body's response to detecting the virus until it produces mass antibodies.

If the (small) number of circulating antibodies are overcome by a large viral load, and if the virus becomes transmissible in a shorter time period, it can "get inside the curve" of antibody response and result in a transmissible infection before the host mounts a full response. Delta is apparently a couple of days 'faster' than the previous Alpha strain in getting to the transmissible stage.

Vaccinated people are much less likely to carry the virus.

Sterilizing or no herd immunity works if you can push R0 below 1. Below 1 fewer and fewer people get infection and the cycle stops.

Actually, herd immunity works if it reduces the R0 to less than 1.

Obviously, the extinction happens a lot faster wit a vaccine as you describe that reduces R0 to zero, but an exponential decline will still result in extinction (barring other reservoirs).

Are there scientific papers out there that are worth reading on the road ahead with what we know about the delta variant? I remember Neil Ferguson’s paper early 2020 that was a goldmine of information and predicted that we would have to do lockdowns on and off for a year and a half til the vaccine. It was pretty spot on.

It depends on what other measures they take. A big part of the problem is everyone said "We're vaccinated, so we're done." That put enormous evolutionary pressure for the virus to learn to hop the vaccine.

That's what I want to know. A mucosal vaccine would be a very effective counter to the ramped up viral load and shorter incubation period that delta has brought.

It's too late to prevent large-scale spread of the virus. That already happened and it's now endemic worldwide. We don't have a time machine.

You obviously can't expect most people to continue tolerating masking, social distancing, and lockdowns indefinitely with no clear, achievable exit criteria. That would be absurd and people in free societies won't comply regardless of the potential consequences. You can complain that they're being irresponsible and putting others at risk but that won't change the reality.

At some point we'll have to accept the risk and move forward with normal life. Fortunately the vaccines are very effective at preventing deaths.

> 1) We need to keep using all strategies - including masking, social distancing, and targeted lockdowns - to reduce large scale spread of the virus. If we don't, we're going to be playing "new variant whack-a-mole" until the end of time.

How long do you think we need to keep using all strategies for? We've been doing that for almost a year and a half now, with no end in sight, despite having a vaccine available to everyone so quickly.

And I suppose you yourself are not at all a self appoiunted internet expert with your broad and highly charged range of opinions without a single clear cut reference backing any of them up?

Worth noting as well is that you're trying to assert a negative without evidence-based substance as part of your particularly alarmist discourse. In effect: We don't know that COVID doesn't cause X list of aweful long term things I just mentioned, though no evidence so far indicates that it does, we should just assume it does however in order to push for a bunch of harsh and punitive measures against those with any skeptical take.

Seasonal flu typically passes and has no lasting or permanent effects, in most cases.

What % of people get Covid and are noticeably operating at less than 100% thereafter? What % are operating at less than 70% thereafter?

Low CFR merely means you didn't die. It doesn't mean Covid didn't break you.

COVID IFR was always low. The CDC planning scenarios (https://www.cdc.gov/coronavirus/2019-ncov/hcp/planning-scena...) consistently showed low IFR for those under 50 even mid 2020 in their earlier updates. However this was obfuscated by alarmist journalism and divisive politics, as well as people confusing CFR and IFR. COVID wasn’t that dangerous ever, unless you were immunocompromised or elderly, or unless your measure of danger is based on a high risk aversion.

There is the possibility of rare lingering side effects. However studies show that the worst side effects, like ARDS, primarily affect those who are obese or vitamin D deficient. You could make an argument that it’s the individual’s’ responsibility to manage their own risks and vulnerability for that. Alternatively you could say that those comorbidities are common enough that they require society wide management.

Massachusetts is reporting 1% CFR for vaccinated individuals.

106/9,969, as of August 7th.

https://www.mass.gov/doc/daily-covid-19-vaccine-report-augus...

I don't believe it's actually the case that once you are infected by the delta strain your body has lasting immunity to that same strain.

It looks like that also is affected by age and other constraints: https://www.nature.com/articles/d41586-020-00502-w

> People who are infected by delta variant will become immune to delta variant

"people who were exposed to H1N1 flu last year will become immune to it, so once it runs its course people will get herd immunity from it and the virus will die out".

that's not how it works. What the scientist is saying here is that it's mutating fast enough that by the time we start to approach "herd immunity" (via vaccination or just exposure) it's mutated and the herd immunity is no longer effective against the new variant. So yeah you're immune to the strain from last year, but it doesn't do anything against this year's strain.

and on top of that Delta is literally so infectious that it'll just about spread right through the existing vaccines. The vaccines were 98% effective against the initial strain, now Pfizer/Moderna are 88% effective, which means you have 6x as much spread (at an epi/population level), on top of a strain that is, itself, 2.5x as transmissible. So now we have to hit a much higher level of vaccination (near-100%) to get the reproduction number under 1.0.

And then you've got the other vaccines - some early studies indicated Astra-Zeneca is only about 60% effective (!) which means even with 100% vaccination that vaccine could not stop the spread. Best-case scenario you have to get those people a booster shot of something else - and the clock is still ticking, it is still mutating and in another year the effectiveness of all the existing vaccines will be even lower.

And on top of that, those are only the "severe illness" numbers, the "mild/moderate" illness numbers are higher, vaccinated people still spread an appreciable amount, and it's spreading through kids very aggressively now (funny how HN told me just last week that kids were immune and we could reopen schools...)

In short if you want vaccines to actually work and reach herd immunity - you have to slow it down enough with containment measures to slow down the rate of mutation. Because if you just let people get exposed, every exposed person is another chance for the virus to mutate, and it's mutating fast enough that by the time we get everyone vaccinated, the virus will have mutated enough the vaccines are no longer very effective.

(And reality check - we've barely got a start on vaccinating the global population, which is what you really have to do to control it. Vaccines are flowing like water in the US and Europe, and to a lesser extent in other developed nations, but in a lot of the world you just can't get a fucking vaccine even if you want one. A few months ago the number was something like 140 countries hadn't even gotten a single dose of vaccine yet.)

Realistically that is no longer possible at this point. People are done with quarantine and social distancing and 40% of the country won't get vaccinated even when they're free and readily available. And now it's mutated to become several times as transmissible - that's game over. It's over, it's going to become endemic, it's a foregone conclusion at this point.

No, they're not. It would be a lot worse without the vaccines.

Just compare how things are going on countries where vaccination is not happening vs countries that have a high population already vaccinated and you will see how ridiculous your comment is. Antivax and comments like this only makes things worse.

They had a ton of COVID cases (1M, in a population of 10M!) and have vaccinated heavily. They're also doing a lot of the social distancing things that they initially avoided.

Vaccination does reduce the chance of spreading the virus. Having 10% of the country get the natural variant and 45% fully immune, plus still doing the social distancing stuff, and requiring negative COVID tests for those entering the country, seems like a pretty good way of keeping delta under control.

Sweden goes into a month-long vacation every July, most business will have 15% or less personnel, people are outside a lot more (and probably out of the cities) if they are in the country.

All of these also helped last year's summer, just look at the graphs, we had a very very normal summertime here, people were going to bars, some clubs, all the parks were crowded and we still got relatively very few infections. Now look at the fall-winter of 2020/2021, massive increase of infections when we aren't on vacations mode anymore and have to stay inside.

Sweden is starting to see an increase of delta-variant cases and by living here and seeing how much people just stopped caring we will definitely see a new wave of infections if delta and/or lambda spread and are really capable of evading the current vaccines.

Please, don't use us as an example if you don't have tacit knowledge of how this society and country works, there are seasonal effects in play that, it seems, you are completely unaware of...