AZ - two doses only due to immunity to the vector?

[AnneofScreamFables]

This quote website and quote have been mentioned on a number of threads but I haven't seen any comment anywhere else (new outlets etc etc).

www.clinicaltrialsarena.com/comment/covid-19-vaccines-antibodies-booster/

Towards the end is this quote "But the drawback with adenovirus-vectored vaccines, in general, is that one can get a maximum of two doses over a lifetime; any more than that and the immune system could generate neutralising antibodies to attack the vector".

Can someone with knowledge shed any light on this? Presumably with all this talk of boosters it either is a problem or it isn't?

This is why AZ doesn't work as well in South Africa, as it is more likely that the people living there have already been infected with the adeno virus in their lifetime.

The Russian vektor vaccine uses two different vectors for this reason.

Someone mentioned this on here a few weeks ago, it may be why the government has ordered 60m doses of Pfizer for the autumn

At this point it is probably best for most people to step back and leave it all to the people who do understand what it all means to make the best decisions for us all!

But basically, this is why we have boosters, different flu formulations every year and constant checks on the efficacy of all medications.

Yes true, vector immunity does mean that future boosters will probably have to be another type, most likely mRNA.

@Peachi82 The reason for lower efficacy in SA is that it’s less effective against the SA variant, not vector immunity. The AZ vaccine uses a chimpanzee adenovirus that people are very unlikely to be immune to. There is only a very low level of cross-immunity between chimp and human adenoviruses too.

So far it looks as though the AZ vaccine is very effective at preventing death and severe disease from SA variant, but not at preventing mild to moderate disease, which is why SA withdrew it.

FictionalCharacter

www.gavi.org/vaccineswork/why-some-people-might-be-immune-certain-covid-19-vaccines

It is hard to tell at the moment, but my statement isn't wrong per se.

@Peachi82

This is why AZ doesn't work as well in South Africa, as it is more likely that the people living there have already been infected with the adeno virus in their lifetime.

The Russian vektor vaccine uses two different vectors for this reason.

Total nonsense!

@AnneofScreamFables

This quote website and quote have been mentioned on a number of threads but I haven't seen any comment anywhere else (new outlets etc etc).

www.clinicaltrialsarena.com/comment/covid-19-vaccines-antibodies-booster/

Towards the end is this quote "But the drawback with adenovirus-vectored vaccines, in general, is that one can get a maximum of two doses over a lifetime; any more than that and the immune system could generate neutralising antibodies to attack the vector".

Can someone with knowledge shed any light on this? Presumably with all this talk of boosters it either is a problem or it isn't?

The "two doses" bit is nonsense.

Yes, there is a risk that the immune system could target the vector - it's why I'd have more faith in the AZ vaccine than the Russian one, although the Russians attempt to get around the problem by using two different vectors - unfortunately both based on the common cold, while the AZ adenovirus is a chimpanzee virus that no human will have encountered before.

So there's a risk that a small number of second doses will be a little less effective due to adenovirus immunity from the first jab. This will increase with each successive jab using the same chimp virus and MAY at some point become a serious problem. Quite when that point will be reached is totally unknown so all we have at the moment is speculation.

@Peachi82

FictionalCharacter

www.gavi.org/vaccineswork/why-some-people-might-be-immune-certain-covid-19-vaccines

It is hard to tell at the moment, but my statement isn't wrong per se.

From your link:

"OVERCOMING ANTI-VECTOR IMMUNITY"

"Yet other companies are using adenoviruses from great apes to reduce this risk. For instance, the University of Oxford/AstraZeneca vaccine uses a chimpanzee adenovirus vector called ChAdOx1, while the Italian biotechnology company ReiThera has opted for an adenovirus that was originally isolated from gorilla faeces"

@AnneofScreamFables can you see why I commented as I did?

Very, very few posters here have an inkling about any of this. But many feel free to comment based on something... and to argue about it.

[quote CuriousaboutSamphire]@AnneofScreamFables can you see why I commented as I did?

Very, very few posters here have an inkling about any of this. But many feel free to comment based on something... and to argue about it.[/quote]
I think it's fine to start a thread with scientific questions about an article, you've just got to appreciate there's a lot of misinformation floating around on mn. On the flip side there are a lot of knowledgeable posters floating around who tend to try and fact check where they can.

Curious yes I can. Fair point. But I saw it in passing in many other threads and wondered - in the hope that there may be someone who can post a clear explanation that other threads could then link to.

Thanks speckled that was exactly my hope. Quite often (not always) a thread develops where very knowledgeable people post explanations or reputable links that can really help understanding.

@speckledostrichegg there are probably 3 posters here that I would trust to make sense of the OPs question. And they don't post on covid threads much more because it became too irritating to continue.

I have a little bit of knowledge, could take a half decent stab at answering OP, but won't because I won't get it 100% correct. And I have seen accidental misinformation catch hold very strongly here.

@AnneofScreamFables I would bet that those other threads are full of conjecture, misinformation and utter guesswork. The language of that article is far more dense than most peole read on a daily basis. Even the trick of replacing each technical work with the name of a fruit doesn't clarify it much - try the fruit trick sometime. It can help make the impenetrable a bit less dense. You at least get the sense of what is working with or against something else (a trick my favourite professor taught me donkey's years ago).

@Peachi82

FictionalCharacter

www.gavi.org/vaccineswork/why-some-people-might-be-immune-certain-covid-19-vaccines

It is hard to tell at the moment, but my statement isn't wrong per se.

Yes I’ve seen that article, but it doesn’t support your statement about why the AZ doesn’t work as well in SA. AZ doesn’t use human Ad5 or Ad26 which a lot of people are immune to. It uses a chimp virus (see last paragraph). I haven’t seen any papers or reliable articles that show vector immunity to be a problem in SA, but I’m happy to be corrected if there is such evidence.

[quote CuriousaboutSamphire]@speckledostrichegg there are probably 3 posters here that I would trust to make sense of the OPs question. And they don't post on covid threads much more because it became too irritating to continue.

I have a little bit of knowledge, could take a half decent stab at answering OP, but won't because I won't get it 100% correct. And I have seen accidental misinformation catch hold very strongly here.

@AnneofScreamFables I would bet that those other threads are full of conjecture, misinformation and utter guesswork. The language of that article is far more dense than most peole read on a daily basis. Even the trick of replacing each technical work with the name of a fruit doesn't clarify it much - try the fruit trick sometime. It can help make the impenetrable a bit less dense. You at least get the sense of what is working with or against something else (a trick my favourite professor taught me donkey's years ago).[/quote]
Yes as I said scientific misinformation is rife on mn. But I don't think that automatically means all threads asking questions about scientific aspects of COVID should be shut down- there are far more than 3 knowledgeable posters knocking around.

Far more pernicious are a) the threads asking for medical advice (i.e stopping medication after vaccination, taking aspirin after vaccination, I have x medical history, should i be vaccinated etc, and b) the threads asserting scientific misinformation as fact instead of opening a discussion

there are far more than 3 knowledgeable posters knocking around. That's not quite the same thing. I am quite knowlegeable but wouldn't say I'd do a good job on the article in the OP. Personally I would trust only 2 or 3 posters here. Based on what I have seen them post and explain.

But that's by the by. And yes to you 2nd paragraph! Abso-bloody-lutely!

My main point was that now, at this point in the vaccination programme, the published papers are becoming ever more esoteric. Maybe it's time to step back and trust in the experts again!

Can I just add - that article in the OP is from June 2020, before vaccine rollout. It’s based on what was known at the time. There is a lot of real-life data now that millions of people have been vaccinated with a number of different vaccine types. There is intensive research on vaccinated people and it’s yielding info every day. It’s likely there will be future changes to the vaccination regimes based on the findings. For now, the vaccination programme is definitely having a positive impact, with death and serious illness massively reduced in vaccinated people.

???

Ooopps! Academic Sin #1

Check the date and the attributions first