Incidence of Viral Rebound After Treatment With Nirmatrelvir-Ritonavir and Molnupiravir. 12/6/22. Wong GL. JAMA Netw Open.

To better understand the much-discussed rebound phenomena when COVID-19 patients receive oral antiviral medication (molnupiravir (Lagevrio) or nirmatrelvir-ritonavir (Paxlovid)), 12,629 adult COVID-19 inpatients in Hong Kong were followed with RT-PCR testing during the first three months of 2022. Serial cycle threshold (Ct) values were used to measure rebound, defined as a Ct value that increased to greater than 40, followed by a decrease to 40 or less. Viral rebound was uncommon, occurring in 0.6% of patients who did not receive an antiviral (n=11,688), 0.8% in molnupiravir patients (n=746), and 1% in nirmatrelvir-ritonavir patients (n=195). Viral rebound was not associated with an increased risk of mortality.

SAB Comment: It’s important to note that this study evaluates viral and not symptom rebound in hospitalized patients. Clinical symptoms were not studied. This study is similar to a research letter previously presented in newsletter 148. Both show a low incidence of viral rebound in treated as well as untreated patients. One study of the mechanism of rebound suggests that a more robust immune response rather than uncontrolled viral replication is the cause of clinical rebound.

https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2799218