Can nirmatrelvir/ritonavir treatment shorten the duration of COVID-19 isolation?

Background: The impact of nirmatrelvir/ritonavir treatment on shedding of viable virus in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is unclear.

Methods: A prospective cohort study evaluating mildly ill COVID-19 patients was conducted. Virologic responses were compared between nirmatrelvir/ritonavir-treatment and supportive care groups. Risk factors and relevant clinical factors for shedding of viable virus were investigated.

Results: A total of 80 COVID-19 patients were enrolled and 222 sputum specimens were collected. Ten patients were dropped during follow-up, and 33 patients in the nirmatrelvir/ritonavir and 37 in the supportive care groups were compared. The median age was 67 years, and 67% were male. Clinical characteristics were similar between groups. Viral loads decreased significantly faster in the nirmatrelvir/ritonavir group compared with the supportive care group ( < 0.001), and the slope was significantly steeper (-2.99 ± 1.54 vs. -1.44 ± 1.52; < 0.001). The duration of viable virus shedding was not statistically different between groups. In the multivariable analyses evaluating all collected specimens, male gender (OR 2.51, 95% CI 1.25-5.03, = 0.010), symptom score (OR 1.41, 95% CI 1.07-1.87, = 0.015), days from symptom onset (OR 0.72, 95% CI 0.59-0.88, = 0.002), complete vaccination (OR 0.09, 95% CI 0.01-0.87, = 0.038), and BA.2 subtype (OR 0.49, 95% CI 0.26-0.91, = 0.025) were independently associated with viable viral shedding, while nirmatrelvir/ritonavir treatment was not.

Conclusion: Nirmatrelvir/ritonavir treatment effectively reduced viral loads of SARS-CoV-2 Omicron variants but did not decrease the duration of viable virus shedding.