Screening of healthcare workers for SARS-CoV-2 highlights the role of asymptomatic carriage in COVID-19 transmission
- Cambridge University Hospitals NHS Trust, United Kingdom
- University of Cambridge, United Kingdom
- Public Health England (PHE), United Kingdom
- National Institutes for Health Research, United Kingdom
Abstract
Significant differences exist in the availability of healthcare worker (HCW) SARS-CoV-2 testing between countries, and existing programmes focus on screening symptomatic rather than asymptomatic staff. Over a 3-week period (April 2020), 1,032 asymptomatic HCWs were screened for SARS-CoV-2 in a large UK teaching hospital. Symptomatic staff and symptomatic household contacts were additionally tested. Real-time RT-PCR was used to detect viral RNA from a throat+nose self-swab. 3% of HCWs in the asymptomatic screening group tested positive for SARS-CoV-2. 17/30 (57%) were truly asymptomatic/pauci-symptomatic. 12/30 (40%) had experienced symptoms compatible with coronavirus disease 2019 (COVID-19) >7 days prior to testing, most self-isolating, returning well. Clusters of HCW infection were discovered on two independent wards. Viral genome sequencing showed that the majority of HCWs had the dominant lineage B∙1. Our data demonstrates the utility of comprehensive screening of HCWs with minimal or no symptoms. This approach will be critical for protecting patients and hospital staff.
Data availability
Sequencing data have been deposited in GSAID under accession codes EPI_ISL_433989-EPI_ISL_433992, EPI_ISL_434005, EPI_ISL_433489-EPI_ISL_433497
Article and author information
Author details
Nicholas J Matheson
Funding
Wellcome (108070/Z/15/Z)
- Michael P Weekes
Addenbrooke's Charitable Trust, Cambridge University Hospitals
- Paul J Lehner
Medical Research Council (MR/P008801/1)
- Nicholas J Matheson
NHS Blood and Transplant (WPA15-02)
- Nicholas J Matheson
National Institute for Health Research (Cambridge Biomedical Research Centre)
- John R Bradley
National Institute for Health Research (Cambridge Biomedical Research Centre)
- M Estee Torok
National Institute for Health Research (Cambridge Biomedical Research Centre)
- Afzal Chaudhry
National Institute for Health Research (Cambridge Biomedical Research Centre)
- Gordon Dougan
Academy of Medical Sciences (Clinician Scientist Fellowship)
- M Estee Torok
Engineering and Physical Sciences Research Council (EP/P031447/1)
- Richard J Samworth
Engineering and Physical Sciences Research Council (EP/N031938/1)
- Richard J Samworth
Wellcome (215515/Z/19/Z)
- Stephen Baker
Cancer Research UK (PRECISION Grand Challenge C38317/A24043)
- Jamie Young
Wellcome (207498?Z/17/Z)
- Ian G Goodfellow
Wellcome (206298/B/17/Z)
- Ian G Goodfellow
Wellcome (210688/Z/18/Z)
- Paul J Lehner
Wellcome (200871/Z/16/Z)
- Kenneth G C Smith
Addenbrooke's Charitable Trust, Cambridge University Hospitals
- Michael P Weekes
Addenbrooke's Charitable Trust, Cambridge University Hospitals
- Stephen Baker
Addenbrooke's Charitable Trust, Cambridge University Hospitals
- Ian G Goodfellow
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Human subjects: As a study of healthcare-associated infections, this investigation is exempt from requiring ethical approval under Section 251 of the NHS Act 2006 (see also the NHS Health Research Authority algorithm, available at http://www.hra-decisiontools.org.uk/research/, which concludes that no formal ethical approval is required). Written consent was obtained from each HCW described in the anonymised case vignettes.
Copyright
© 2020, Rivett et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Screening of healthcare workers for SARS-CoV-2 highlights the role of asymptomatic carriage in COVID-19 transmission
eLife 9:e58728.
https://doi.org/10.7554/eLife.58728
Further reading
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- Epidemiology and Global Health
- Microbiology and Infectious Disease
The BNT162b2 mRNA COVID-19 vaccine (Pfizer-BioNTech) is being utilised internationally for mass COVID-19 vaccination. Evidence of single-dose protection against symptomatic disease has encouraged some countries to opt for delayed booster doses of BNT162b2, but the effect of this strategy on rates of asymptomatic SARS-CoV-2 infection remains unknown. We previously demonstrated frequent pauci- and asymptomatic SARS-CoV-2 infection amongst healthcare workers (HCWs) during the UK’s first wave of the COVID-19 pandemic, using a comprehensive PCR-based HCW screening programme (Rivett et al., 2020; Jones et al., 2020). Here, we evaluate the effect of first-dose BNT162b2 vaccination on test positivity rates and find a fourfold reduction in asymptomatic infection amongst HCWs ≥12 days post-vaccination. These data provide real-world evidence of short-term protection against asymptomatic SARS-CoV-2 infection following a single dose of BNT162b2 vaccine, suggesting that mass first-dose vaccination will reduce SARS-CoV-2 transmission, as well as the burden of COVID-19 disease.
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- Epidemiology and Global Health
- Medicine
Previously, we showed that 3% (31/1032)of asymptomatic healthcare workers (HCWs) from a large teaching hospital in Cambridge, UK, tested positive for SARS-CoV-2 in April 2020. About 15% (26/169) HCWs with symptoms of coronavirus disease 2019 (COVID-19) also tested positive for SARS-CoV-2 (Rivett et al., 2020). Here, we show that the proportion of both asymptomatic and symptomatic HCWs testing positive for SARS-CoV-2 rapidly declined to near-zero between 25th April and 24th May 2020, corresponding to a decline in patient admissions with COVID-19 during the ongoing UK ‘lockdown’. These data demonstrate how infection prevention and control measures including staff testing may help prevent hospitals from becoming independent ‘hubs’ of SARS-CoV-2 transmission, and illustrate how, with appropriate precautions, organizations in other sectors may be able to resume on-site work safely.
