Evaluating the impact on health outcomes of an event that resulted in a delay in contact tracing of COVID-19 cases in England, September 2020: an observational study

Lucy Findlater; Livia Pierotti; Charlie Turner; Adrian Wensley; Cong Chen; Shaun Seaman; Pantelis Samartsidis; Andre Charlett; Charlotte Anderson; Gareth Hughes; Matthew Hickman; Obaghe Edeghere; Isabel Oliver

doi:10.1136/bmjopen-2022-064982

Evaluating the impact on health outcomes of an event that resulted in a delay in contact tracing of COVID-19 cases in England, September 2020: an observational study

BMJ Open. 2023 Oct 12;13(10):e064982. doi: 10.1136/bmjopen-2022-064982.

Authors

Affiliations

¹ UK Health Security Agency South of England, Bristol, UK.
² Population Health Sciences, University of Bristol, Bristol, UK livia.pierotti@bristol.ac.uk.
³ UK Health Security Agency East of England, Cambridge, UK.
⁴ UK Health Security Agency North of England, Leeds, UK.
⁵ MRC Biostatistics Unit, Cambridge, UK.
⁶ UK Health Security Agency, London, UK.
⁷ Population Health Sciences, University of Bristol, Bristol, UK.
⁸ UK Health Security Agency Midlands and East of England, Birmingham, UK.

Abstract

Objective: In September 2020, 15 861 SARS-CoV-2 case records failed to upload from the Second Generation Surveillance System (SGSS) to the Contact Tracing Advisory Service (CTAS) tool, delaying the contact tracing of these cases. This study used CTAS data to determine the impact of this delay on population health outcomes: transmission events, hospitalisations and mortality. Previously, a modelling study suggested a substantial impact.

Design: Observational study.

Setting: England.

Population: Individuals testing positive for SARS-CoV-2 and their reported contacts.

Main outcome measures: Secondary attack rates (SARs), hospitalisations and deaths among primary and secondary contacts were calculated, compared with all other concurrent, unaffected cases. Affected SGSS records were matched to CTAS records. Successive contacts and cases were identified and matched to hospital episode and mortality outcomes.

Results: Initiation of contact tracing was delayed by 3 days on average in the primary cases in the delay group (6 days) compared with the control group (3 days). This was associated with lower completion of contact tracing: 80% (95% CI: 79% to 81%) in delay group and 83% (95% CI: 83% to 84%) in control group. There was some evidence to suggest increased transmission to non-household contacts among those affected by the delay. The SAR for non-household contacts was higher among secondary contacts in the delay group than the control group (delay group: 7.9%, 95% CI: 6.5% to 9.2%; control group: 5.9%, 95% CI: 5.3% to 6.6%). There did not appear to be a significant difference between the delay and control groups in the odds of hospitalisation (crude OR: 1.1 (95% CI: 0.9 to 1.2)) or death (crude OR: 0.7 (95% CI: 0.1 to 4.0)) among secondary contacts.

Conclusions: Our analysis suggests that the delay in contact tracing had a limited impact on population health outcomes; however, contact tracing was not completed for all individuals, so some transmission events might not be captured.

Keywords: COVID-19; EPIDEMIOLOGY; INFECTIOUS DISEASES; PUBLIC HEALTH.

Publication types

Observational Study
Research Support, Non-U.S. Gov't

MeSH terms

COVID-19* / epidemiology
COVID-19* / prevention & control
Contact Tracing / methods
England / epidemiology
Humans
Outcome Assessment, Health Care
SARS-CoV-2

Abstract

Publication types

MeSH terms

Grants and funding