There’s some speculation that people with long haul COVID have difficulty completely clearing the infection. That for some reason, it remains present and active within certain tissues causing problems. When they get vaccinated, the immune system kicks into high gear thinking there’s a massive attack underway, and that may help clear most or all of the remaining infection.
It’s just speculation at this point. What’s real are all the stories of people with long haul COVID who have gotten relief after vaccination. It definitely seems to help in a lot of cases. About 20% of hospitalized cases result in long haul COVID, and some moderate cases do as well. A friend of mine developed major back problems during a moderate bout of COVID which didn’t go away when she “recovered”. This is a middle-aged woman who was previously very healthy and active. Getting vaccinated a few months after helped her a lot. Not quite to 100%, but close enough and she’s finally able to go back to all the things she enjoyed doing previously.
Kind of reminds me of people who have rheumatoid arthritis; who, when they get bee stings, their bodies’ reactions to the sting helps their arthritis feel better.
I’ve wondered about latent brushfire covid for a while that unless the the immune systems get kicked into high gear by vaccines, then the virus stays latent in certain tissues or joints causing mischief.