Duration of Infectious Virus Shedding by SARS-CoV-2 Omicron Variant–Infected Vaccinees

Kenichiro Takahashi; Masahiro Ishikane; Mugen Ujiie; Noriko Iwamoto; Nobumasa Okumura; Testsuro Sato; Maki Nagashima; Ataru Moriya; Michiyo Suzuki; Masayuki Hojo; Takayuki Kanno; Shinji Saito; Sho Miyamoto; Akira Ainai; Minoru Tobiume; Takeshi Arashiro; Tsuguto Fujimoto; Tomoya Saito; Masaya Yamato; Tadaki Suzuki; Norio Ohmagari


Emerging Infectious Diseases. 2022;28(5):998-1001. 

In This Article

Abstract and Introduction


To determine virus shedding duration, we examined clinical samples collected from the upper respiratory tracts of persons infected with severe acute respiratory syndrome coronavirus 2 Omicron variant in Japan during November 29–December 18, 2021. Vaccinees with mild or asymptomatic infection shed infectious virus 6–9 days after onset or diagnosis, even after symptom resolution.


The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant of concern belonging to the Pango lineage B.1.1.529, known as the Omicron variant, has spread rapidly worldwide.[1,2] Several reports describe high infectivity and transmissibility of Omicron.[3,4] The clinical course and the duration of virus shedding based on cycle quantification (Cq) values among 11 Omicron-infected patients has been reported.[5] However, the relationship between duration of virus shedding and infectivity of Omicron is unknown. To help determine the criteria for patient isolation, we evaluated the duration of shedding of Omicron variant virus isolated from upper respiratory samples collected from the reported case-patients in Japan.

This study was approved by the ethics committee of the National Center for Global Health and Medicine (approval no. NCGM-G-003472–03) and the Medical Research Ethics Committee of the National Institute of Infectious Diseases (NIID) for the use of human subjects (approval no. 1178). We obtained written informed consent to publish the article.