I'm double jabbed with AZ. Am I right in thinking my booster won't actually be a booster?

[HollywoodTease]

I'm struggling a bit to get my head around this, and not sure if I have understood correctly so please bear with me. I'm looking to put my thoughts down in writing and then for wiser heads than mine to have a look at my thinking and tell me if I have misunderstood.

When the vaccines were developed and for the first round of vaccines, the 2 main ones used in the UK were AZ and Pfizer. But despite them both having similar efficacy, they are different in composition and in HOW they protect against the virus. AZ, unlike both Pfizer and Moderna, is not an mRNA.

So we have 2 vaccines, both effective, but that work differently in the body to produce antibodies. A first dose provides a certain level of protection, a second one essentially doubles down on that and ups the protection level. So far so good.

So getting on to boosters. If you've had your 2 doses of Pfizer or Moderna then a booster is just that. It's a further dose of the same thing to make it work more effectively. That makes sense to me.

But if your first 2 doses were AZ, then giving a dose of Pfizer or Moderna surely can't boost your immunity, because it provides immunity in a different way so there isn't anything already there for it to boost.

So effectively if I am double-jabbed with AZ and now go for my booster what I am getting isn't a booster, it's a first dose of a new vaccine. See above, first doses of any of the vaccines give some immunity but need a 2nd dose to be fully effective. In which case to have the best chance at immunity should I be getting a second one within the 8-12 week timeline?

Have I over-thought this, or am I right? That my booster won't be a booster as although I do (hopefully) have some immunity from my 2 AZ doses, it's a different kind of immunity obtained by a different method?

Or is immunity immunity and it doesn't matter how your body produces an immune response to covid as long as it produces one?

I'm so confused!

I get what you're saying, but I thought the evidence for mixing vaccines was actually quite positive?

It all turns into antibodies so id say immunity is immunity.

You are overthinking this. The third jab will boost the immunity that you’ve got from your first two.

Lots of studies show you get better immunity from mixing vaccines.

See above, first doses of any of the vaccines give some immunity but need a 2nd dose to be fully effective. In which case to have the best chance at immunity should I be getting a second one within the 8-12 week timeline?

Are you asking if you need a fourth jab?

No you’re not right and the evidence is in the CovBoost trial results which show why boosting with Pfizer after AZ produces good results.
Have your booster

It is a booster. The different vaccines all provoke immunity, by different mechanisms but it’s still an immune response by your body. A booster with any vaccine provokes more antibodies, and however the antibodies were provoked, the protective effect when the virus comes along is the same.

There is tons of evidence from trials that whichever vaccines are used, there is a boosting effect. @AlexaShutUp is correct.

Besides, if this didn’t work, this dosing regime wouldn’t be approved. It would just be a waste of vaccine.

The problem with repeated boosters with AZ is the risk of vector immunity- immunity to the “carrier” virus that the vaccine is based on. This isn’t an issue with RNA vaccines because they contain no virus particles of any kind.

But if your first 2 doses were AZ, then giving a dose of Pfizer or Moderna surely can't boost your immunity, because it provides immunity in a different way so there isn't anything already there for it to boost.

You're muddled up. The immunity isn't to the vaccine. The immunity is to the spike protein on the virus. The vaccine is just a way of getting that spike protein to you without infecting you with the virus, so your body can learn what to do with it.

You haven’t understood the science of vaccines. As a pp said, the vaccine doesn’t directly give you immunity, the purpose of the vaccine is to help your body learn how to tackle the disease. It’s excellent you are getting Pfizer- the evidence says that mixing vaccines is particularly effective. The more different ways that your immune system learns to tackle the virus the better.

All the vaccines are presenting the same stimulus to your immune system (the spike protein). The difference is just in how it’s presented. So a booster will work just fine whichever vaccine type it is.

Have a look at this www.nature.com/articles/d41586-021-02853-4

I agree OP. And I've just been pondering this all week as I've just had my invitation for my 'booster' which is not a booster.

@chinateapot

All the vaccines are presenting the same stimulus to your immune system (the spike protein). The difference is just in how it’s presented. So a booster will work just fine whichever vaccine type it is.

But if you have Pfizer, then you need 2 jabs, but this is not being offered.

But if your first 2 doses were AZ, then giving a dose of Pfizer or Moderna surely can't boost your immunity, because it provides immunity in a different way so there isn't anything already there for it to boost.

No, that's incorrect. It will still boost your immunity. What you need is antibody production (and T and B memory cells, hopefully). Whether you get those via AZ, Pfizer or another vaccine is immaterial.

But you could say the all the Pfizer jabbed people need 2 doses of AZ now to cover all bases.

I've had 2 AZ then Covid, so why not throw in a Pfizer too.

If you've had 2 AZ then caught actual real covid, then surely that's the best immunity.

@thenightsky

If you've had 2 AZ then caught actual real covid, then surely that's the best immunity.

I've been trying to research this, as that's my situation and I'm not eligible for a booster. It seems that your immunity will probably be very good if you caught covid and then got double jabbed, but they don't seem to have enough data yet to be able to say whether the same applies when the order is reversed. I'm certainly hoping so!

How i see it is similar to different people having different learning styles.

So imagine a teacher explaining a new concept to a class. The teacher will ideally explain this in a few different ways, so if you are a visual learner vs an auditory learner then the concept will be explained to cover both, and one explanation will mean more to each person.

The vaccine is the same, the more ways that you 'explain' to your body about the virus, the higher the chance that it'll 'learn' what it needs to.

Thank you, I obviously don't understand how vaccines work! Chinateapot that was a very informative article.

So I've been looking at it wrongly.

What you are all telling me is that any vaccine gives my body the tools to provoke an immune response to covid. However, the strength of that response can wane over time. Therefore a further vaccine isn't boosting the way the initial vaccine works it's boosting my body's potential immune response to the virus.

I think I'm getting it?

@thenightsky

If you've had 2 AZ then caught actual real covid, then surely that's the best immunity.

This has not yet been established. Data is being collected.

I think Pfizer followed by AZ did not produce as good a response as vice verse, so that’s why AZ isn’t generally being used for boosters in this country.

I have had two doses of AZ.
DH recently caught Covid, and although i felt mildly unwell and i was obviously fighting something off, I didn’t test positive . (I had daily LFTs and three PCR tests over the period DH was unwell, all negative).
Will this close exposure to Covid have acted as a booster ?

This is really interesting
So what do you think about people that have had triple Pfizer out of interest? Less well protected than those with AZ plus Pfizer?

@HollywoodTease that's it.

Think of it like learning a foreign language.

In French, cheese is 'fromage'.

You can learn that by me telling you. I might have to tell you a few times, because humans are lousy at remembering stuff.

Or you can learn it by going to the supermarket, and seeing the word written on a sign over the cheese counter. You'd probably have to do this a few times, because humans are lousy...

The stimulus is very different but, whether you learn it formally or buy seeing the word in use, the end result is that your brain learns what fromage means.

If I told you a couple of times, and then took you to the supermarket, you wouldn't be relearning from scratch. The supermarket trip would consolidate the learning I'd already given you. So you might only need one supermarket trip to make the word sink in.

It's basically the same with this. Your immune system is learning what a spike protein is, that it's a threat, and how to kill it. It really doesn't matter how it's shown that spike protein. What matters is the repeated teaching.

Does that help at all?

Oh yes that's a great analogy, thank you!

So I have been looking at it from the wrong way around. I'm looking at the actual vaccine as the important thing, thinking that how it triggers an immune response is important. When actually it's my body's response to the virus that counts. It doesn't matter what method I use to trigger the required response, just that my body is able to respond. And the more ways my body learns to recognise the virus and respond to it the better protection I will have?

That also makes sense in terms of getting a better response with mixing the vaccines too doesn't it?