Investigation of an outbreak of symptomatic SARS-CoV-2 VOC 202012/01-lineage B.1.1.7 infection in healthcare workers, Italy

Clin Microbiol Infect. 2021 Aug;27(8):1174.e1-1174.e4. doi: 10.1016/j.cmi.2021.05.007. Epub 2021 May 10.

Abstract

Objectives: In December 2020, Italy began a national immunization campaign using the BNT162b2 coronavirus disease 2019 (COVID-19) mRNA vaccine, prioritizing healthcare workers (HCWs). Immune serum from vaccinated subjects seems (largely) to retain titres of neutralizing antibodies, even against severe acute respiratory syndrome coronavirus 2 (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).

Methods: Two physicians and one nurse working on the same shift on 20th February 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).

Results: 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).

Conclusions: 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.

Keywords: COVID-19; Healthcare workers; Outbreak; SARS-CoV-2 VOC 202012/01-LINEAGE B.1.1.7; Vaccine; Whole-genome sequencing.

MeSH terms

  • Adult
  • BNT162 Vaccine
  • COVID-19 / epidemiology*
  • COVID-19 / transmission
  • COVID-19 / virology
  • COVID-19 Vaccines / administration & dosage*
  • Disease Outbreaks*
  • Female
  • Health Personnel
  • Humans
  • Immunoglobulin G / blood
  • Intubation, Intratracheal
  • Italy / epidemiology
  • Male
  • Middle Aged
  • Personal Protective Equipment
  • Phylogeny
  • SARS-CoV-2 / genetics*
  • SARS-CoV-2 / immunology*
  • Vaccination*
  • Whole Genome Sequencing

Substances

  • COVID-19 Vaccines
  • Immunoglobulin G
  • BNT162 Vaccine