This may or may not be related. So I'm adding this in comment instead of main post. 2 people very close to me got COVID vaccine 2nd shot and I had 39°C fever with severe headache and few other flu like symptoms. (but no coughing).
I've had very virtually zero contact with strangers. I live a super introverted life. I'm feeling much better after 2 days. I actively avoided doing PCR. Why? Try these reasons: