Clinical Features of Patients with COVID-19 Recurrence During Hospitalization in the Omicron Variant Surge.

Background: Repeat positive results for SARS-CoV-2 by antigen detection test/RT-PCR in recovered COVID-19 patients were not very rare even when omicron variants became dominant, but the clinical features of patients with recurrent COVID-19 during hospitalization are still unclear. Methods: The clinical characteristics of patients with recurrent COVID-19 during hospitalization were retrospectively investigated from January 2023 to December 2023. Results: Recurrence of COVID-19 was found in 7 of 275 (2.5%) patients during hospitalization. Their mean age was 80.3 (74-89) years, and 4 of 7 (57.1%) patients were hospitalized on the hematology ward with B cell/non-Hodgkin lymphoma. These 4 lymphoma patients had been vaccinated, but the other 3 patients hospitalized on the emergency ward and the neurology ward had not been vaccinated. Of the 7 patients, 6 (85.7%) were initially treated with remdesivir (RDV), but only 3 patients were re-treated with RDV, and the other 4 patients were successfully re-treated with oral 3C-like protease inhibitors, such as ensitrelvir (ESV) and nirmatrelvir/ritonavir (N/R). Conclusion: These data suggest that COVID-19 recurrence was found in patients with hematological disorders, such as lymphoma, and/or patients with no vaccination history. However, these patients were treated successfully by re-administration of anti-SARS-CoV-2 agents, including ESV and N/R.