https://www.scientificamerican.com/article/why-the-u-s-is-underestimating-covid-reinfection/

Kaitlyn Romoser first caught covid-19 in March, likely on a trip to Denmark and Sweden, just as the scope of the pandemic was becoming clear. Romoser, who is 23 and a laboratory researcher in College Station, Texas, tested positive and had a few days of mild, coldlike symptoms.

In the weeks that followed, she bounced back to what felt like a full recovery. She even got another test, which was negative, in order to join a study as one of the earliest donors of convalescent blood plasma in a bid to help others.