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Outbreak investigation of symptomatic SARS-COV-2 VOC 202012/01-lineage B.1.1.7 infection in healthcare workers, Italy.

  • Loconsole, Daniela1
  • Sallustio, Anna2
  • Accogli, Marisa1
  • Leaci, Angela3
  • Sanguedolce, Antonio4
  • Parisi, Antonio5
  • Chironna, Maria6
  • 1 Department of Biomedical Sciences and Human Oncology-Hygiene Section, University of Bari, Bari, Italy. , (Italy)
  • 2 Azienda Ospedaliero-Universitaria Consorziale Policlinico di Bari, Bari, Italy. , (Italy)
  • 3 San Paolo Hospital, Bari, Italy. , (Italy)
  • 4 Local Health Unit of Bari, Italy. , (Italy)
  • 5 Istituto Zooprofilattico Sperimentale della Puglia e della Basilicata, Foggia, Italy. , (Italy)
  • 6 Department of Biomedical Sciences and Human Oncology-Hygiene Section, University of Bari, Bari, Italy. Electronic address: [email protected] , (Italy)
Published Article
Clinical Microbiology and Infection
Publication Date
May 10, 2021
DOI: 10.1016/j.cmi.2021.05.007
PMID: 33984489


In December 2020, Italy began a national immunization campaign using the BNT162b2 mRNA COVID-19 vaccine, prioritizing healthcare workers (HCWs). Immune serum from vaccinated subjects seems to (largely) retain titres of neutralizing antibodies, even against SARS-CoV-2 VOC 202012/01-lineage B.1.1.7. Here, we describe an outbreak of SARS-CoV-2 lineage B.1.1.7 infection in three HCWs in a hospital setting; two of the HCWs were fully vaccinated (i.e., had received two doses). Two physicians and one nurse working on the same shift on February 20, 2021, were involved in the outbreak. Real-time PCR, antigen tests, and serological tests for the IgG anti-spike protein of SARS-CoV-2 were performed, along with whole-genome sequencing (WGS). SARS-CoV-2 infection was confirmed in all three HCWs; all presented with mild symptoms of COVID-19. The two physicians were fully vaccinated with BNT162b2 vaccine, with the second dose administered 1 month before symptom onset. Both had high titres of IgG anti-spike antibodies at the time of diagnosis. WGS confirmed that all virus strains were VOC 202012/01-lineage B.1.1.7, suggesting a common source of exposure. Epidemiological investigation revealed that the suspected source was a SARS-CoV-2-positive patient who required endotracheal intubation due to severe COVID-19. All procedures were carried out using a full suite of personal protective equipment (PPE). This mini-outbreak highlights some important issues about the efficacy of vaccines against transmission of SARS-CoV-2 variants, the high risk of exposure among HCWs, and the need for optimized implementation of PPE in hospitals. The wide circulation of VOC 202012/01 in Europe and Italy highlights the need to improve surveillance and genetic sequencing. Copyright © 2021. Published by Elsevier Ltd.

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