The side effect was confirmed, but it remained unclear how common it was.
Now, an observational study of patients being treated for acute COVID-19 in a multicenter healthcare system suggested that virologic rebound occurs in about 20% of patients treated with N-R, marketed as Paxlovid, versus about 2% of those who did not receive treatment. The results were published in Annals of Internal Medicine.”
The study was conducted by researchers from Massachusetts General Hospital and Brigham and Women’s Hospital and involved 127 patients with acute COVID-19. The frequency of virologic rebound in 72 patients with and 55 patients without N-R treatment was compared.
The study outcome was defined as viral rebound (VR) within 3 weeks of an initial positive test, which was either a positive SARS-CoV-2 viral culture following a prior negative culture or sustained elevated viral load after a prior decline. The recipients of N-R were older, had received more COVID-19 vaccinations, and more commonly had immunosuppression.
The results indicated that 15 participants (20.8%) taking N-R had VR versus one (1.8%) who was untreated (absolute difference, 19.0 percentage points; 95% CI, 9.0-29.0 percentage points; P = .001). All persons with VR had a positive viral culture result after a prior negative result.
“In multivariable models, only N-R use was associated with VR (adjusted odds ratio, 10.02 [CI, 1.13 to 88.74]; P = 0.038),” the authors pointed out. “Virologic rebound was more common among those who started therapy within 2 days of symptom onset (26.3%) than among those who started 2 or more days after symptom onset (0%) (P = 0.030). Among participants receiving N-R, those who had VR had prolonged shedding of replication-competent virus compared with those who did not have VR (median, 14 vs. 3 days). Eight of 16 participants (50% [CI, 25% to 75%]) with VR also reported symptom rebound; 2 were completely asymptomatic. No post-VR resistance mutations were detected.”
The researchers recommend that their findings be factored into consideration when weighing the benefits and risks of N-R treatment in patients at low risk for severe disease. They pointed out that for patients at moderate-to-high risk for severe COVID-19, the clinical benefits associated with N-R use are well established.
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