Somewhat OT...
>>symptoms
A friend and his family are part of a blood study where they have blood drawn every so often to test for antibodies. It turned out that his daughter (early 20s) got Covid twice without knowing it. The first time she had a small antibody response and a much bigger one the second time, but never any symptoms and did not pass it to her parents or sister (though her sister, who is in her last year of medical school, managed to get Covid all on her own... no surprise there).