Modelling the risk of SARS-CoV-2 infection through PPE doffing in a hospital environment

Marco Felipe King, Amanda M. Wilson, Mark H. Weir, Martín López-García, Jessica Proctor, Waseem Hiwar, Amirul Khan, Louise A. Fletcher, P. Andrew Sleigh, Ian Clifton, Stephanie J. Dancer, Mark Wilcox, Kelly A. Reynolds, Catherine J. Noakes

Research output: Contribution to journalArticlepeer-review


Self-contamination during doffing of personal protective equipment (PPE) is a concern for healthcare workers (HCW) following SARS-CoV-2 positive patient care. Staff may subconsciously become contaminated through improper glove removal, so quantifying this risk is critical for safe working procedures. HCW surface contact sequences on a respiratory ward were modelled using a discrete-time Markov chin for: IV-drip care, blood pressure monitoring and doctors’ rounds. Accretion of viral RNA on gloves during care was modelled using a stochastic recurrence relation. The HCW then doffed PPE and contaminated themselves in a fraction of cases based on increasing case load. The risk of infection from this exposure was quantified using a dose-response methodology. A parametric study was conducted to analyse the effect of: 1a) increasing patient numbers on the ward, 1b) the proportion of COVID-19 cases, 2) the length of a shift and 3) the probability of touching contaminated PPE. The driving factors for infection risk were surface contamination and number of surface contacts. HCWs on a 100% COVID-19 ward were less than 2-fold more at risk than on a 50% COVID ward (1.6% vs 1%), whilst on a 5% COVID-19 ward, the risk dropped to 0.1% per shift (sd=0.6%). IV-drip care resulted in higher risk than blood pressure monitoring (1.1% vs 1% p<0.0001), whilst doctors’ rounds produced a 0.6% risk (sd=0.8%). Recommendations include supervised PPE doffing procedures such as the “doffing buddy” scheme, maximising hand hygiene compliance post-doffing and targeted surface cleaning for surfaces away from the patient vicinity.

Original languageEnglish (US)
JournalUnknown Journal
StatePublished - Sep 23 2020


  • COVID-19
  • Hospital infection model
  • PPE
  • Quantitative microbial risk assessment (QMRA)
  • SARS CoV-2
  • Surface contact transmission

ASJC Scopus subject areas

  • Medicine(all)

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