Few patients experience rebound of COVID-19 symptoms after nirmatrelvir/ritonavir (NM/R) treatment, according to research published online June 14 in Clinical Infectious Diseases.

Nischal Ranganath, M.D., Ph.D., from the Mayo Clinic in Rochester, Minnesota, and colleagues conducted a among who received NM/R for mild-to-moderate severe acute respiratory syndrome coronavirus 2. Data were included for 483 patients (, 63 years) who had a high risk for severe disease progression. Overall, 93 percent of the patients were fully vaccinated.

The researchers found that four of the patients (0.8 percent) experienced symptom rebound, defined as recurrence of COVID-19 symptoms following successful completion of five days of NM/R therapy, at a median of nine days after NM/R treatment. All four were fully vaccinated. None of the patients required hospitalization, and all improved without further treatment.

"Rebound after NM/R treatment is uncommon in our population of high-risk, but mostly nonimmunocompromised [patients]," the authors write. "Among the patients who developed rebound of symptoms after NM/R treatment, the clinical presentation was mild and did not require COVID-19 directed therapies."

More information: Nischal Ranganath et al, Rebound Phenomenon after Nirmatrelvir/Ritonavir Treatment of Coronavirus Disease-2019 in High-Risk Persons, Clinical Infectious Diseases (2022). DOI: 10.1093/cid/ciac481

Journal information: Clinical Infectious Diseases