In these cases, a patient diagnosed with Covid-19 was typically prescribed Paxlovid, took it, felt better, perhaps even tested negative, and then suddenly tested positive days or even more than a week later. For some, the resurgences were asymptomatic. But for others, they were as bad or worse than the original illness.

“There were a lot of symptoms associated with the rebound, actually, almost as much as there was for the original infection,” said Davey Smith, an infectious disease specialist at UC San Diego who recently documented one such case. “Headache, fatigue, cough.”…

Pfizer’s clinical trials found rebound in only 1 to 2% of patients and it occurred in both placebo and treatment groups. Many infectious disease specialists believe that in the real world, it is much higher, but that could be driven in part by the number of influential physicians and researchers on Twitter who have experienced rebound.

“We’re in that era where people all post their health information on a website,” said Monica Gandhi, an infectious disease physician at UC San Francisco. “It’s very hard to distinguish perception from reality.”