SARS-CoV-2 Virologic Rebound With Nirmatrelvir-Ritonavir Therapy : An Observational Study.

Abstract

Data are conflicting regarding an association between treatment of acute COVID-19 with nirmatrelvir-ritonavir (N-R) and virologic rebound (VR). To compare the frequency of VR in patients with and without N-R treatment for acute COVID-19. Observational cohort study. Multicenter health care system in Boston, Massachusetts. Ambulatory adults with acute COVID-19 with and without use of N-R. Receipt of 5 days of N-R treatment versus no COVID-19 therapy. The primary outcome was VR, defined as either a positive SARS-CoV-2 viral culture result after a prior negative result or 2 consecutive viral loads above 4.0 log₁₀ copies/mL that were also at least 1.0 log₁₀ copies/mL higher than a prior viral load below 4.0 log₁₀ copies/mL. Compared with untreated persons (<i>n</i> = 55), those taking N-R (<i>n</i> = 72) were older, received more COVID-19 vaccinations, and more commonly had immunosuppression. Fifteen participants (20.8%) taking N-R had VR versus 1 (1.8%) who was untreated (absolute difference, 19.0 percentage points [95% CI, 9.0 to 29.0 percentage points]; <i>P</i> = 0.001). 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]; <i>P</i> = 0.038). 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%) (<i>P</i> = 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. Observational study design with differences between the treated and untreated groups; positive viral culture result was used as a surrogate marker for risk for ongoing viral transmission. Virologic rebound occurred in approximately 1 in 5 people taking N-R, often without symptom rebound, and was associated with shedding of replication-competent virus. National Institutes of Health.