(HealthDay News) — Patients with COVID-19 may experience viral and symptom rebound more often than previously reported, according to research published in Clinical Infectious Diseases.

The researchers observed viral and symptom rebound among patients treated with nirmatrelvir plus ritonavir (Paxlovid) and among untreated patients.

The team compared the epidemiology of rebound in Paxlovid-treated and untreated patients with acute COVID-19 who were clinically eligible for Paxlovid. The patients were assigned to the treatment group (n=127) or control group (n=43) based on their decision to take Paxlovid and were asked to test with a rapid antigen test on a regular schedule for 16 days.

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The incidence of symptom rebound was 18.9% in the Paxlovid group and 7.0% in the control group (P =.06). The incidence of viral rebound was 14.2% in the Paxlovid group and 9.3% in the control group (P =.41).

There were no notable differences in viral rebound based on age, gender, preexisting conditions, or major symptom groups during the acute phase or at 1 month.

“This preliminary report suggests that rebound after clearance of test positivity or symptom resolution is higher than previously reported,” the study authors wrote. “Large studies with diverse participants and extended follow-up are needed to better understand the rebound phenomena.”

Two authors disclosed financial ties to the biopharmaceutical industry.

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