Characterization of Virologic Rebound Following Nirmatrelvir-Ritonavir Treatment for Coronavirus Disease 2019 (COVID-19)

Clin Infect Dis. 2023 Feb 8;76(3):e526-e529. doi: 10.1093/cid/ciac512.


We enrolled 7 individuals with recurrent symptoms or antigen test conversion following nirmatrelvir-ritonavir treatment. High viral loads (median 6.1 log10 copies/mL) were detected after rebound for a median of 17 days after initial diagnosis. Three had culturable virus for up to 16 days after initial diagnosis. No known resistance-associated mutations were identified.

Keywords: COVID-19; anti-virals; nirmatrelvir-ritonavir; therapeutics; virology.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • COVID-19 Drug Treatment
  • COVID-19*
  • Humans
  • Mutation
  • Ritonavir / therapeutic use


  • nirmatrelvir
  • Ritonavir