Testing positive for COVID-19 after getting the vaccine?

[editor]

I'm posting this here as I'm a bit confused. Yesterday my antigen test came in as positive, but this website says;

The only ways you could test positive on a PCR test after being vaccinated would be if you were one of the rare cases where the vaccine didn’t protect you from infection, or if you got a false positive test result. The COVID-19 vaccines currently being rolled out are extremely effective, with most able to prevent at least 95% of infections, with only a small percentage of ‘breakthrough’ infections occurring. These are typical with other vaccines too.

For COVID-19, so far these kinds of infection seem to be extremely rare, with one US Centers for Disease Control and Prevention (CDC) report showing that breakthrough infections happened in only 0.1% of fully vaccinated people, and only 2% of those died.

The vaccine causes your immune system to produce antibodies, which could in theory show up as positive on an antibody test. Even if you believe you had never been infected, this result could also mean you had previously been infected with COVID-19 and been asymptomatic, and so cannot be relied upon to indicate that the vaccine has caused immunity. In addition, even when your body does produce antibodies after vaccination, they can take a few weeks to build up and then levels can drop off again, so they may be present in undetectable quantities that don’t show up on an antigen test.

Gavi, the Vaccine Alliance

Gavi is an international organisation created in 2000 to improve access to new and underused vaccines for children living in the world's poorest countries.

www.gavi.org

About the source GAVI - Wikipedia

*corrected to say I took the antigen test

 

[cupid_stunt]

The COVID-19 vaccines currently being rolled out are extremely effective, with most able to prevent at least 95% of infections

Well, that bit is bollocks, they do offer around 95% protection against severe infection / hospitalisation, not against infection.

 

[Kevbad the Bad]

This is a related question, I believe. If you have been double jabbed, and therefore probably have antibodies, can it be detected in any way whether you have actually had Covid asymptomatically at some time?

 

[elbows]

Disregard the tone of that website editor, they've just laid it on a bit thick because they think an overly positive message is useful to the cause. This happens a lot with matters related to vaccines because various authorities and experts are desperate not to put people off or encourage defeatism etc. When they dont quite get the balance right, hype related credibility erosion becomes a risk.

The fact is that a large chunk of the people that models expect to be infected in this wave have been vaccinated. And there are no shortage of stories about vaccinated people testing positive.

This would have happened to an extent without the Delta variant, and we'd expect Delta to make those numbers larger still.

Even when it comes to areas where vaccines are even more useful and effective, such as keeping people out of hospital, they expect large percentages of hospitalised people to have been vaccinated. Thats just the way it goes when the vaccine isnt 100% effective and really huge numbers of people have been vacinated - a very small percentage of a very large number is still quite a lot of people.

 

[elbows]

This is a related question, I believe. If you have been double jabbed, and therefore probably have antibodies, can it be detected in any way whether you have actually had Covid asymptomatically at some time?

In general yes, there are some ways to tell the difference, although I wouldnt claim that the results will be spot on for every single person.

eg:

Nucleoprotein (Roche N) assays only detect post-infection antibodies, whereas spike (Roche S) assays will detect both post-infection antibodies and vaccine-induced antibodies. Thus, changes in seropositivity for the Roche N assay will reflect the effect of natural infection. Increases in seropositivity as measured by S antibody will reflect both infection and vaccination. Antibody responses to both targets will reflect infection or vaccination occurring at least 2 to 3 weeks previously given the time taken to generate a COVID-19 antibody response. Donors have been asked to defer donations for 7 days post vaccination.

Thats from the weekly surveillance report.

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1000373/Weekly_Flu_and_COVID-19_report_w27.pdf

 

[2hats]

In general yes, there are some ways to tell the difference, although I wouldnt claim that the results will be spot on for every single person.

Antibody tests for N and S will only differentiate between past infection and vaccinees for vaccines approved thus far by the UK regulator. Those tests wouldn't reliably discriminate between convalescents and persons receiving whole virion inactivated vaccines - Covaxin, CoronaVac, Valneva, for example (or live attenuated vaccines eg COVI-VAC, though none regulatory approved yet AFAIK) - which might be the case this autumn as/when/if such vaccines are improved here (and already won't be the case for some persons in/from other regulatory jurisdictions).

I'm not entirely clear what the original question is...

Yes, you can still get infected after partial or complete vaccination.

No, vaccination with currently (UK) approved vaccines has no bearing on PCR test outcome (though one could imagine the potential for a false positive PCR test if taken immediately after administration of an intra-nasal live attenuated vaccine, for example).

 

[elbows]

Antibody tests for N and S will only differentiate between past infection and vaccinees for vaccines approved thus far by the UK regulator. Those tests wouldn't reliably discriminate between convalescents and persons receiving whole virion inactivated vaccines - Covaxin, CoronaVac, Valneva, for example (or live attenuated vaccines eg COVI-VAC, though none regulatory approved yet AFAIK) - which might be the case this autumn as/when/if such vaccines are improved here (and already won't be the case for some persons in/from other regulatory jurisdictions).

Cheers for the interesting info. So in a nutshell we (UK) can spot the difference so far because the vaccines we've used so far only feature the spike part? So the bit I quoted earlier does include the core ingredient of this detail but it can go unnoticed unless explicitly explained as you have done.

 

[kalidarkone]

Two things editor ...

On another thread you said you did an antibody test that came up positive....did you mean pcr test? Cus I'm guessing if you are vaccinated you would expect to have a positive antibody test.

Secondly....anecdotally I have heard several reports of people who are doubly vaccinated being positive for the delta variant.

 

[elbows]

I think he said antigen test, not antibody test.

 

[wemakeyousoundb]

the short answer is
yes

 

[elbows]

Yeah like I said even on the sharp end we expect positive cases in vacinated people, eg hospitalised people. Last week my local hospital had 10 Covid patients - 4 had no doses of vaccine, one had 1 dose, 5 had 2 doses. All tested positive. Numbers will be far greater for people infected but not hospitalised.

 

[kalidarkone]

I think he said antigen test, not antibody test.

Oh yeh he did...my bad

 

[elbows]

Oh yeh he did...my bad

Its an easy mistake to make - a pandemic of jargon!

 

[elbows]

Since being vaccinated is expected to reduce symptoms for many, its even more important now that people dont assume that something mild is not Covid.

eg one of the downsides to vaccination is that there may be more asymptomatic or 'cant really tell if these are symptoms' cases these days.

There might also have been questions about whether testing may miss more cases, eg if viral load is much lower. But since we have Delta now, and some studies implied viral loads a thousand times greater for Delta, perhaps these things have balanced out somewhat at this stage.

 

[2hats]

Cheers for the interesting info. So in a nutshell we (UK) can spot the difference so far because the vaccines we've used so far only feature the spike part? So the bit I quoted earlier does include the core ingredient of this detail but it can go unnoticed unless explicitly explained as you have done.

If you expose the immune system to the entire virus (inactivated or attenuated, or indeed natural infection) then you can see all kinds of antibodies - to epitopes in nucleocapsid, membrane, ORF, non-structural proteins as well as spike. The vaccines approved in the UK thus far all target (encode for) spike (largely as this is thought to be the most antigenic and most likely to generate both binding and neutralising antibody responses).

Antibody tests to N tend not to be as high a specificity as antibody tests to S1/2.

 

[xenon]

I was wondering about this the other day, the degree of sterilisation the current vaccines offer. i.e. the ability to prevent becoming infected in the first place. All the talk about their efficacy has focused on the effectiveness in keeping the symptoms and any illness to the minor end of things.

So even when the whole adult population is vaccinated, it seems like we'll still be going around catching it, spreading it, though perhaps at a much reduced level, until what, we also gain a level of immunity via infection. And by these ways reduce the R rate.

In short what is the evidence for sterilisation capability in these current vaccines.

 

[elbows]

If you expose the immune system to the entire virus (inactivated or attenuated) then you can see all kinds of antibodies - to epitopes in nucleocapsid, membrane, ORF, non-structural proteins as well as spike. The vaccines approved in the UK thus far all target (encode for) spike.

Cheers, yes, all makes sense to me, I was just guilty of not explicitly pointing it out. I'm so glad you are here in this pandemic and want to take this opportunity to praise your important contributions. Partly because I often rather water down the science in a potentially sloppy way, and you dont.

 

[elbows]

I was wondering about this the other day, the degree of sterilisation the current vaccines offer. i.e. the ability to prevent becoming infected in the first place. All the talk about their efficacy has focused on the effectiveness in keeping the symptoms and any illness to the minor end of things.

So even when the whole adult population is vaccinated, it seems like we'll still be going around catching it, spreading it, though perhaps at a much reduced level, until what, we also gain a level of immunity via infection. And by these ways reduce the R rate.

In short what is the evidence for sterilisation capability in these current vaccines.

Broadly speaking the focus and the estimates atarted with the most severe end of things, death prevention, then moved onto hospitalisation, then level of symptoms, then ability to get infected, then ability to pass it on.

As time has gone on, estimates have become available for more of these, but still with plenty of uncertainty. And it comes up more in public discussion these days, for example someone asked a question about vaccine ability to prevent transmission in yesterdays press conference, and there were some attempts to answer that question. I'm afraid I dont feel like transcribing that bit from the press conference right now, but I probably can fish out some estimates if you are interested.

Certainly such analysis gets complicated when too many variables are changed at once - they've had to recalculate all this stuff for the Delta variant, for example, and they have to try to spot the difference between changes in one direction due to vaccines, and changes in the other direction de to variants and the removal of rules governing behaviour and contacts and what settings are open for business.

Some of this is also reflected in advice, eg I think they've told the clinically vulnerable people who shielded previously to think carefully about avoiding certain settings and avoiding contact with people who arent double-jabbed.

 

[editor]

Just did a second antibody test and that came up positive.
I've also just done a PCR test and that's been sent off.

Sorry for my earlier confusion over that tests I'd done. All this terminology is a bit confusing!

So today I feel alright - coughing a bit and a bit bunged up but the kind of thing that in a normal year, I would have shrugged off as a bit of a cold. I'm hoping I'm over the worst now...

 

[elbows]

Oh the bit I do remember clearly from yesterdays press conference is that they put together a few numbers to come up with a rough estimate that three quarters of vaccinated people wont be in a position to pass the virus on. But then Whitty pointed out that this still means a quarter of vaccinated people could pass it on.

 

[elbows]

Just did a second antibody test and that came up positive.
I've also just done a PCR test and that's been sent off.

Sorry for my earlier confusion over that tests I'd done. All this terminology is a bit confusing!

So today I feel alright - coughing a bit and a bit bunged up but the kind of thing that in a normal year, I would have shrugged it off a a a bit of a cold. I'm hoping I'm over the worst now...

I'd like to thank you for doing the right thing.

And yes in regards attitudes towards mild illness in pre-pandemic times, this reminds me of a converation we had here at the start of the pandemic about assumptions about things like 'proper flu' vs 'man flu' and how unsafe such assumptions are. Its inevitable that a big chunk of our perceptions are based on severity of symptoms, but in reality its a poor guide and this is one of the reasons I want the future to involve far more testing for illnesses rather than guesswork.

 

[elbows]

Speaking of which, I dont go on about the public health campaigns in much detail but I do know that "dont guess, get a test" has been one of the cental themes they've been using in a range of adverts this year. There is a whole series of these, here are just a couple:

One limitation with this sort of campaign is that the UK stuck to an absurdly narrow list of symptoms, which are likely to be missing even more cases in this vaccine era.

 

[xenon]

Oh the bit I do remember clearly from yesterdays press conference is that they put together a few numbers to come up with a rough estimate that three quarters of vaccinated people wont be in a position to pass the virus on. But then Whitty pointed out that this still means a quarter of vaccinated people could pass it on.

Thanks. As you say above, we'll get more evidence over time I suppose.

And of course it's great if 75% of vaccinated people can't pass the virus on but out of roughly 50 million UK adults who will have been that's still 12.5 million.

 

[elbows]

Thanks. As you say above, we'll get more evidence over time I suppose.

And of course it's great if 75% of vaccinated people can't pass the virus on but out of roughly 50 million UK adults who will have been that's still 12.5 million.

Yes, plus when looking at the actual detail, estimates for various things tend to be different for Pfizer and AZ. Headline figures most often mentioned to the public tend to involve merging these into a single number rather than dwelling publicly on the prospects that all vaccines are not created equal. But all the modelling does tend to take account of the differences and how many people got which vaccine in this country.

Chuck this stuff in with a load of other estimates and unknowns and we end up with the very broad range of possibilities for how the current wave will unfold.

For example what the authorities would ultimately hope for is a level of population immunity and other impact from vaccines and prior infections resulting in a situation where there isnt much potential for really large waves to happen in future. The Delta variant changes the equations in terms of when they might expect to hit some ultimate threshold of herd immunity, if thats even possible. Because of Delta they arent as optimistic about that as they once were, and the whole thing is a big mess of factors. If this current wave should happen to peak sooner and at lower levels than they dare to hope for at this stage, then some of their estimates havent been positive enough. But variables that can lead to this are not just about vaccines and immunity, but also human behaviour when faced with a wave and government approach that makes a lot of people uncomfortable. I dont know as we'll ever end up with a tidy answer to all of these things, and of course immunity can change over time, not to mention future variants.

 

[2hats]

In short what is the evidence for sterilisation capability in these current vaccines.

Some. For SARS-CoV-2 this is highly likely to differ with the variant concerned.

The role of vaccines is primarily to reduce disease, not infection. For a small number of pathogen/disease combinations they are also, conveniently, sterilising, but few vaccines produce 100% sterilising immunity (eg HPV). It's pretty typical for there to only be degrees of sterilising immunity or even next to none at all. Also bear in mind that this degree of sterilising immunity (for SARS-CoV-2) varies over time (initially rises but then will diminish with time after vaccination) and varies from person to person.

 

[elbows]

And in theory if symptom severity and clarity/ability to guess accurately is reduced via vaccination, spread potential can actually get worse in a vaccine era. Especially if too many people think its all over.

 

[WouldBe]

The problem I can see with swabs is they will pickup anything in your nose or throat wether you will react to it or not. Just because you've detected virus in the swab doesn't mean you're infected just as pollen doesn't mean you have hayfever. Or am I missing something?

 

[2hats]

If there is sufficient viral RNA in the swab to be detected within N cycles (N<<40) then, yes, you are/have been infected*: virus is replicating in your upper respiratory tract (though the stage of infection - early/mid/late/post - isn't clear without multiple tests, at least daily, if not more frequently).

* assuming no contamination during sample collection, lab analysis.

 

[elbows]

And for more info on what cycle means in that context, see stuff like this:

What’s a PCR test cycle threshold and why it matters - Full Fact

It’s been falsely claimed the WHO said PCR tests are flawed. It said “weak positive” cases with high “cycle thresholds” may need to be retested.

fullfact.org

 

[editor]

I have a conundrum. When I reported my test result I could only input the previous day for when I had symptoms, but they'd actually started up on the Thursday - which means I could possibly come out of isolation quicker. I've been told I could ring up and get this sorted but I've just spend 25 mins getting nowhere. Anyone have any ideas?