Nosocomial Outbreak by Delta Variant From a Fully Vaccinated Patient

Jiwon Jung, Jungmin Lee, Heedo Park, Young Ju Lim, Eun Ok Kim, Man Seong Park, Sung Han Kim

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


Background: The potential for a nosocomial outbreak of coronavirus disease 2019 (COVID-19) from a fully vaccinated individual is largely unknown. Methods: In October 2021, during the time when the delta variant was dominant, a nosocomial outbreak of COVID-19 occurred in two wards in a tertiary care hospital in Seoul, Korea. We performed airflow investigations and whole-genome sequencing (WGS) of the virus. Results: The index patient developed symptoms 1 day after admission, and was diagnosed with COVID-19 on day 4 post-admission. He was fully vaccinated (ChAdOx1 nCoV-19) 2 months before the diagnosis. Three inpatients and a caregiver in the same room, two inpatients in an adjacent room, two inpatients in rooms remote from the index room, and one nurse on the ward tested positive. Also, two resident doctors who stayed in an on-call room located on the same ward tested positive (although they had no close contact), as well as a caregiver who stayed on an adjacent ward, and a healthcare worker who had casual contact with this caregiver. Samples from five individuals were available for WGS, and all showed < 1 single-nucleotide polymorphism difference. CCTV footage showed that the index case walked frequently in the corridors of two wards. An airflow study showed that the air from the corridor flowed into the resident on-call room, driven by an air circulator that was always turned on. Conclusion: Transmission of severe acute respiratory syndrome coronavirus 2 from a fully vaccinated index occurred rapidly via the wards and on-call room. Care must be taken to not use equipment that can change the airflow.

Original languageEnglish
Pages (from-to)1-8
Number of pages8
JournalJournal of Korean medical science
Issue number17
Publication statusPublished - 2022

Bibliographical note

Funding Information:
This study was supported by grants from the Korea Advanced Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT, Republic of Korea (grant No. 2020M3H8A1115041), and from the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT, Republic of Korea (NRF-2017M3A9E4061995).

Publisher Copyright:
© 2022. The Korean Academy of Medical Sciences. All Rights Reserved.


  • Airborne Transmission
  • COVID-19
  • SARS- CoV-2
  • Vaccination

ASJC Scopus subject areas

  • Medicine(all)


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