Someone I know got the Pfizer vaccine on the same day that they were exposed to the actual virus - contact with someone who tested positive. 5 days later this person tested positive so obviously they isolated but weren't particularly ill with it.
Is this person likely to have got any benefit from the vaccine or will the body's reaction to the actual virus mean that they are effectively no more protected than someone unvaccinated who has been infected and recovered?
I know that the vaccine is supposed to take 2 weeks to reach full effectiveness but during the relevant 2 weeks they were fighting off the actual virus not responding to the vaccine mechanism.
I think I understand that the vaccine works by forcing cells to make something that looks a bit like covid, which the immune system can then attack. Surely that mechanism is affected by there being genuine covid infection in the body at the same time? Can anyone with a better understanding of vaccine science than me explain? (I am a scientist but a totally different field)