What’s the science behind allowing fully vaccinated people more freedoms?

[SparklesandGold]

I’m fully vaccinated and I do think if people can get vaccinated then they absolutely should but obviously if someone decides not to then that’s their own business.

I don’t agree with this nonsense of excluding unvaccinated people from doing certain things.

Is there any scientific evidence to back that up? Does being fully vaccinated actually reduce someone spreading the virus if they have it?

Hmmm.. would people be ok with unvaccinated tourists entering the UK? Since apparently there is no difference between vaxxed and unvaxxed people.

"Vaccination reduces the likelihood of transmission yes."

Not according to the CDC

@someusernameorother

"Vaccination reduces the likelihood of transmission yes."

Not according to the CDC

Can you share the source for this? Are they talking about secondary transmission only?

From the CDC website (last updated 6 August):

Unvaccinated people remain the greatest concern: Although breakthrough infections happen much less often than infections in unvaccinated people, individuals infected with the Delta variant, including fully vaccinated people with symptomatic breakthrough infections, can transmit it to others. CDC is continuing to assess data on whether fully vaccinated people with asymptomatic breakthrough infections can transmit. However, the greatest risk of transmission is among unvaccinated people who are much more likely to contract, and therefore transmit the virus.

Fully vaccinated people with Delta variant breakthrough infections can spread the virus to others. However, vaccinated people appear to be infectious for a shorter period: Previous variants typically produced less virus in the body of infected fully vaccinated people (breakthrough infections) than in unvaccinated people. In contrast, the Delta variant seems to produce the same high amount of virus in both unvaccinated and fully vaccinated people. However, like other variants, the amount of virus produced by Delta breakthrough infections in fully vaccinated people also goes down faster than infections in unvaccinated people. This means fully vaccinated people are likely infectious for less time than unvaccinated people.

www.nature.com/articles/d41586-021-02187-1

Either way, vaccinated and unvaccinated people are catching and spreading the virus to vaccinated and unvaccinated people. If this is about controlling spread, then the argument for vaccine passports is nullified.

Either way, vaccinated and unvaccinated people are catching and spreading the virus to vaccinated and unvaccinated people. If this is about controlling spread, then the argument for vaccine passports is nullified.

Ok, first, the article you linked to doesn’t support your statement that the CDC doesn’t agree with the statement that vaccination reduces the likelihood of transmission.

But I also don’t agree with the conclusion you’ve drawn from the fact that both vaccinated and unvaccinated people are able to spread the virus if infected. Your argument only stands if both groups are both infected and transmit onwards at identical rates. However that certainly isn’t the case for the first, and it’s an uncertain picture for the second. But with the first alone, even with delta, the risk is more than halved.

If we’re looking to control the spread, the obvious thing to do is have measures to reduce the R0. It’s well established that in a vaccinated group, even if some have the virus, many fewer will be infected as a result, and will therefore not create onward chains of transmission.

That’s without considering whether those who are vaccinated but infected are a lower risk overall, as the Singapore study quoted in the Nature article you linked to suggested based on clearance rates, and as Imperial have suggested for asymptomatic infection.

In fact, if your goal was to control transmission at a certain level, vaccine passports are going to be something to consider.

If you’re looking to eliminate transmission, I agree it’s fairly useless. But if you’re looking to create fewer onward chains of transmission at higher risk events and venues, limiting it to a population with an effective R0 of 3 rather than 7 is quite a logical approach.

@JassyRadlett you’re assuming that all unvaccinated are not immune.

[quote bumbleymummy]@JassyRadlett you’re assuming that all unvaccinated are not immune.[/quote]
No; vaccinated and unvaccinated people as groups, regardless of prior infection, present different risks of infection and secondary transmission. The data is pretty clear on that.

I’m not against the idea of immunity passports rather than vaccine passports (and tbh I don’t have strong views on vaccine passports full stop.)

But my point was that, at a population level, vaccine passports are not an irrational way to reduce or control spread and the PP’s statement was not supported by the facts.

There are many other factors that need to be taken into account to become policy, but as a pure public health measure to control the spread of the virus in high risk situations, limiting access to those who are vaccinated is a rational way to reduce the rate of transmission in those places.

Do you have links to the data showing that an immune person after previous infection is more of a risk for transmission than a vaccinated person?

@bumbleymummy

Do you have links to the data showing that an immune person after previous infection is more of a risk for transmission than a vaccinated person?

I never said they were.

Ok. What did you mean by this then?

vaccinated and unvaccinated people as groups, regardless of prior infection, present different risks of infection and secondary transmission. The data is pretty clear on that.

@bumbleymummy

Ok. What did you mean by this then?

vaccinated and unvaccinated people as groups, regardless of prior infection, present different risks of infection and secondary transmission. The data is pretty clear on that.

Exactly what it says.

As a group, vaccinated people, including those with a poor immune response to the vaccine, present a different level of risk to unvaccinated people, including those with top-notch virus-acquired immunity as a group.

As groups they are discrete and easily identifiable at an individual level based on public health data, so from a pure public health perspective, only looking at the goal of controlling spread (the PP’s scenario to which I was responding), vaccine passports for high-risk situations are an effective tool.

As I’ve said, I think there are broader considerations beyond ‘will this reduce the rate of community or population level transmission’, and rightly so. But that’s not what I

It would be elegant to have data on actual immunity that you could base it on. But I suspect it’s a fool’s errand not only because we know immunity of all kinds changes over time, but because it would require regular testing, and extra paperwork and I don’t think we have totally clear picture yet on what level of immunity you need to prevent future infection.

You’ll note that nowhere in my post did I talk about the risk posed by individuals in different circumstances rather than the collective risk of two different groups, and impacts at a population level on the rate of community transmission.

As a group, vaccinated people, including those with a poor immune response to the vaccine, present a different level of risk to unvaccinated people, including those with top-notch virus-acquired immunity as a group.

Ok. What do you think the differences in level of risk are and what data are you basing it on? You said the ‘data is pretty clear’.

Yep. Loads of data.

REACT is a good starting point, which I imagine you’ve looked at as it was mentioned upthread. It’s a good source as it’s not just looking at symptomatic infection so gives a better picture of overall risk of spread from each group. The latest survey wave found double vaccinated people were three times less likely to be infected, and were also less likely to become infected after close contact with an infected person.

(REACT also found suggestions in their data that double vaccinated people may be less likely to transmit the virus onwards than unvaccinated people).

But there’s loads around, from around the world, on the relative infection rates of vaccinated people as a group versus unvaccinated people as a group. That’s were we get the vaccine efficacy data from. You can try Lopez et al in the NEJM, the CIRN paper out of Canada, the PHE surveillance reports.

When your baseline is ‘this group is 50-60% less likely to get infected’, the relative risk of spread from that group versus the control group is fairly easy to see. You halve your R0 immediately, without any of the other factors for which data is sketchier.

Why would you bundle ‘immune after infection’ unvaccinated people with non-immune unvaccinated people and compare them all as a group to vaccinated people though?

@bumbleymummy

Why would you bundle ‘immune after infection’ unvaccinated people with non-immune unvaccinated people and compare them all as a group to vaccinated people though?

I haven’t ‘bundled’ it like that, those collecting the data have.

Though I did set out above why it would be rational from a pure public health perspective it to consider it through this lens.

I can’t speak for why those doing the research have ‘bundled’ them that way in the presentation of their data, of course.

Regardless, this is the data I am referring to when you ask me about the relative risk of the vaccinated group (with all its many and varied members in terms of immune response) and the unvaccinated (ditto).

Ok, change it to: why would someone bundle them together?

Considering the recent studies showing durable immunity after infection, it may be something that needs to be re-examined.

I said, ‘you are assuming all unvaccinated are not immune’ and you replied:

No; vaccinated and unvaccinated people as groups, regardless of prior infection, present different risks of infection and secondary transmission.

It does seem as if you are suggesting that one group is more of a risk than the other. But if a proportion of the unvaccinated group is immune after infection then their risk of contracting and transmitting the virus is different to unvaccinated people who are not immune. And if the data you are presenting is purely based on non-immune unvaccinated people then it’s not taking natural immunity into account.

Sorry, can you give a few examples of "freedoms" given to vaccinated people that those not vaccinated are excluded from?

As I’ve already said, I can’t speak for why researchers have done this but I did give one view upthread.

It does seem as if you are suggesting that one group is more of a risk than the other.

I’m not just suggesting it. It’s factual based on current data, looking at the two groups as a whole.

But if a proportion of the unvaccinated group is immune after infection then their risk of contracting and transmitting the virus is different to unvaccinated people who are not immune.

Indeed. And as I’ve also said, there will be people in the vaccinated group who have poor or no immunity. As I’ve said repeatedly, I was commenting on what the data says about those two groups and their overall collective risk, not variation of individuals within those groups.

And if the data you are presenting is purely based on non-immune unvaccinated people then it’s not taking natural immunity into account.

It isn’t. It’s based on all unvaccinated people, including those with immunity, just as the vaccinated group includes those in whom the vaccine was ineffective. Vaccination status is a static and easily available data point; immunity status is not. Despite including people with virus-acquired immunity, the unvaccinated group still presents a much higher risk of infection and therefore of community-level onward transmission.

When you reflect on the fact that the unvaccinated group includes some people who have virus-acquired immunity, it makes the performance of the vaccine in studies like REACT-1 look even more impressive.

I know the data isn’t measuring what you’d like it to measure, and I’ve given my own view on immunity status versus vaccination status upthread. But this is what the data says about these two discrete groups.

Ok, I’m not really sure that comparing all vaccinated with all unvaccinated without is particularly helpful tbh. There is plenty of evidence now that shows durable immunity after infection. We don’t know how many immune unvaccinated there are in the groups or how many non-immune vaccinated there are. It would really need to be broken down further into previously infected (who may or may not be immune) and vaccinated(who may or may not be immune). If there is no significant difference between them irt transmission risk then previously infected people should be treated the same as vaccinated.

I don’t take issue with any of what you’ve said. I’m not sure why you’re saying it to me, though. You asked for the data backing up my statements on the relative risks of vaccinated people as a group versus unvaccinated people as a group. I provided it.

Like it or not, from a public health perspective vaccination status is a lot simpler than immunity status, which is one reason public health authorities around the world will be looking at vaccination status as an option for future (or current in some countries) public health measures.

As I said, I’d the goal was elimination it would be pretty useless but if the goal is population level control then (despite variation of individual risk within both groups) then from a pure public health standpoint having two discrete groups for which individual public health data already exists, one of which has a dramatically lower risk profile than the other, presents quite an elegant option for reducing spread in higher risk situations. That’s why it’s on the table for authorities around the world.

I’ve already provided my views on immunity status versus vaccination status and on vaccine passports; I’m not going to repeat them.

I’ve provided the data you asked for. I didn’t collect it, I didn’t make the decisions about what those studies report on - and the fact you don’t like what the data is measuring really isn’t my problem to solve.

@JassyRadlett my first reply to you was simply that you were assuming that all unvaccinated were not immune. (I know it’s not you personally but I meant what you were referring to) And you replied,

No; vaccinated and unvaccinated people as groups, regardless of prior infection, present different risks of infection and secondary transmission. The data is pretty clear on that.

But it looks like the data you’re referring to is bundling all unvaccinated into the same group without any info about whether or not they’ve been previously infected. So treating all unvaccinated as if they are not immune. I’ve said why I don’t think this is accurate/helpful above.

Like it or not, from a public health perspective vaccination status is a lot simpler than immunity status

Is it though? If the studies are showing that immunity after infection is durable in the majority then presuming immunity after infection is not really much different to presuming immunity after vaccination. Proof of a positive test is accepted as proof of previous infection for the green pass. We already assume that people above a certain age are immune to some diseases - measles, mumps etc even though they weren’t vaccinated against them.

I’m not trying to have a go at you personally btw! Sorry if it’s coming across like that. I’m just discussing the data that’s available and the decisions being made irt it. I don’t think it’s your problem to solve by any means :)

It wouldn’t be a surprise that the government are hoping for herd immunity, that’s generally the whole point of vaccination.
The earlier problem was that they were applying the herd immunity concept, which is at the core of the concept of mass vaccination, to immunity after infection, which isn’t actually a thing and unsurprisingly didn’t work.

But it looks like the data you’re referring to is bundling all unvaccinated into the same group without any info about whether or not they’ve been previously infected. So treating all unvaccinated as if they are not immune. I’ve said why I don’t think this is accurate/helpful above.

No, you're drawing an inference there that doesn't exist. These studies do not treat all unvaccinated people as if they are not immune. They simply report on the relative infection rates and risk of the vaccinated and unvaccinated groups, with all the variation in immunity that lie within them. Suggesting otherwise is false.

Is it though? If the studies are showing that immunity after infection is durable in the majority then presuming immunity after infection is not really much different to presuming immunity after vaccination. Proof of a positive test is accepted as proof of previous infection for the green pass. We already assume that people above a certain age are immune to some diseases - measles, mumps etc even though they weren’t vaccinated against them.

It's already simpler if only because vaccination data exists; immunity data doesn't. So even if you don't consider variations in immunity levels across both groups and a lack of firm data on what level of antibodies confers protection, you've already got existing datasets that are easily identifiable at an individual level and for which there is clear data at a population level. From a public policy perspective, you always look for existing reliable data first.

So, say your policy goal is to halve the level of overall Covid transmission. You've already got a way to identify vaccinated vs unvaccinated people. You have data that shows that the vaccinated people as a group are much lower risk. If you're a policymaker, a vaccine passport would be an attractive option based on that alone.

As I said, immunity may be a fairer and more elegant solution. But it certainly isn't simpler from this starting point.

@3womeninaboat herd immunity after infection is actually a thing. It just wasn’t advised for coronavirus because it would have resulted in too many hospitalisations/deaths in the most vulnerable groups. Immunity that comes from vaccination or previous infection all contributes to herd immunity. Although apparently it’s not actually going to be possible to achieve herd immunity with delta anyway.