Correlation between vaccine side effects and immune system

[Nunnery]

Sorry if this has been asked before.

There seems to be a huge variation in people’s side effects from the jab, some having no reaction at all through to people still feeling rough weeks later.

Has it been established whether there is any correlation between side effects and how you would have reacted to Covid? Does it mean that if you had a strong reaction to the vaccine that covid itself would have made you very unwell and vice versa?

No reaction - does that mean that you may have already had covid or have antibodies? Or again the other way around? Would you have a strong reaction if you’ve already had covid?

Essentially, is there any relationship between side effects and your immune system?

It seems that older people have less side effects and younger more. I can’t remember where I read this but if your immune system is better (younger) then you are more likely to have a stronger reaction. But this doesn’t also mean the vaccine is ineffective if you have no symptoms.

Everyone I know in 40-50s who has had the vaccine have had a few days of side effects and they have all had Covid previously. Again I read somewhere that if you’ve had covid your body is primed to respond to the vaccine as it recognises the virus and triggers a strong immune response.

I read an article which suggested that, although some people will have a stronger immune response to the vaccine, that doesn't actually mean that they will develop greater immunity to covid - they will typically have the same level of antibodies afterwards as someone who had no side effects.

Essentially, it's like some people's immune systems overreact a bit, but the result is broadly the same either way.

Not sure if that applies to people who have already had covid, though. My understanding is that they will develop stronger immunity after the vaccine, but I'm not an expert so may just be talking rubbish.

It's totally unrelated, and has been stated several times by experts on various programmes. It's become a bit of an urban legend around childhood vaccines, I think because it makes people feel a bit better about putting their babies through it, and it's been translated onto the Covid vaccine. But it means nothing about effectiveness, unfortunately.

I am 51 and had, from what I can gather, a strong reaction to the vaccine. I have not had Covid.

From general Googling and speaking to a few medic professionals I know, the consensus seems to be that this means I have a very active and strong immune system. My system knew it was being attacked and put up a fight, was how someone described it to me. Doesn’t mean I am anymore or less protected than someone who had no symptoms.

When you fall and sprain your ankle, you'll see a number of things happen to your ankle. It will swell, redden and the skin will feel hotter. All of this is your immune system reacting to (in this case) a non-existent invader.

Whenever your body encounters an invader - virus, bacteria, vaccine your immune system responds both usefully, unusefully and sometimes harmfully (e.g. concussion). All you say about the "unuseful" bit is that among those with a weaker immune system, there's likely to be less response in general so you'd expect fewer side effects. Among the rest of the population it means nothing at all - a healthy immune system can have zero side effects or it can have LOTS of side effects.

Separately it's possible that side effects resulting from the immune response to the antigen presented by the vaccine would be the same or worse if presented with covid itself, since the antigen is similar. So perhaps those who have several days of headaches etc after a vaccine can comfort themselves thinking covid would likely have been worse for them. But of course this is conjecture - plausible, but unproven.