Symptom and Viral Rebound in Untreated Covid-19 Infection

ABSTRACT

Background: Rebound of SARS-CoV-2 RNA and symptoms has been reported in people treated with nirmatrelvir/ritonavir. Since the natural course of viral and symptom trajectories during COVID-19 have not been well described, we evaluated the incidence of viral rebound and symptom relapse in untreated individuals with mild-to-moderate COVID-19. Method(s) This analysis included 563 participants randomized to placebo in the ACTIV-2/A5401 platform trial. Participants recorded the severity (scored as 0-3) of each of 13 targeted symptoms daily from days 0-28, with symptom score being the summed score (0-39). Symptom rebound was defined as >=4 point increase in symptom score between the maximum and the preceding minimum score. Anterior nasal (AN) swabs were collected for SARS-CoV-2 RNA testing on days 0-14 and 28. Viral rebound was defined as a >=0.5 log10 RNA copies/mL increase from the immediately preceding time point to a level >=3.0 log10 RNA copies/mL, with high-level rebound defined as an increase of >=0.5 log10 copies/mL to a level >=5.0 log10 RNA copies/mL. To mirror the timing of a 5-day nirmatrelvir/ritonavir course, a supportive analysis was conducted where participants were only classified as rebounders if their rebounds occurred on or after day 5. Result(s) Symptom rebound was identified in 26% of participants at a median [Q1, Q3] of 6 [4, 9] days after study entry and 11 [9, 14] days after initial symptom onset. Individuals with symptom rebound were more likely to be female, at high risk for progression to severe disease, have shorter time since symptom onset at study entry, and have higher symptom score and higher AN viral levels day 0. Viral rebound was detected in 32%, with high-level rebound in 13% of participants. Participants with viral rebound were older, more likely to be at low risk for progression to severe disease and had higher median AN viral level at day 0. Most symptom and viral rebound were transient with 89% of symptom rebound and 95% of viral rebound events occurring for only a single day before improving. The combination of symptom and high-level viral rebound was observed in 3% of participants. In the supportive analysis of rebound occurring >=5 days after study entry, 22% and 20% of participants met symptom and viral rebound criteria, respectively, but only 1.2% of participants met criteria for both symptom and high-level viral rebound. Conclusion(s) Symptom or viral rebound in the absence of antiviral treatment is common, but the combination of symptom and viral rebound is rare.