ROCHESTER, Minn. — Mayo Clinic researchers studied the outcomes of 483 high-risk patients treated for COVID-19 with a five-day oral regimen of nirmatrelvir and ritonavir, together marketed as Paxlovid. Only a handful developed COVID-19 rebound symptoms, and the researchers say more studies are needed to determine why. Overall, the treatment benefited everyone in the study. All recovered, including the patients who developed rebound symptoms, which were generally mild. The findings appear in the journal Clinical…