The questions are getting harder...and this is harder to explain.
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So you get a dose of the virus...and your body should mount a straight forward response...You get ill, and after few days your immune system gets going and takes care of the virus...and you make a recovery. In a couple of weeks you are over it...like a normal cold...( A common cold is caused by a different Corona virus). That is what happens in 70-80 % if cases...some don't even get ill.
What has taken people by surprise is that many people who get serious Covid, or who get prolonged Covid ( longCovid like your wife)... something else goes on.
Everything starts normally, your body raises a response but for some reason the response goes a bit nuclear. Other factors are released. These are called cytokines and give rise to a "cytokine storm ) This is a bit like corporal Jones in dad's army running round panicking and shouting "don't panic, don't panic.
This is a huge destructive response when the immune system is really really worked up and destroys your own body cells that it thinks is hiding the virus...causing destruction of your lungs and other tissue where it thinks the virus is e.g. nervous system, heart and kidneys...the virus also cause your blood to be sticky and that causes the immune cells attack that too.
Some people die from this combination of viral attack and cytokine storm.
It is also why the disease often is seen in two parts...the flu/cold first week,,,that in many marks the full disease....but in some a second week shows a steady decline into breathlessness and ITU.
Many people get over the cytokine storm second week...but are left with residual damage that may take months to years to repair.
So finally the doctor is suggesting that your wife should be wary of the vaccine as it could once again over stimulate the already hyperactive immune system again.
In people who have seen the virus but just raised an ordinary response.....this will not be a problem...as the immune system has already learnt to control the response.
I hope that makes some sense