Contact Tracing for COVID-19

Last Updated: June 1, 2020

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This Briefing Note was completed by the Research, Analysis, and Evaluation Branch (Ministry of Health) based on information provided by members of the COVID-19 Evidence Synthesis Network. Please refer to the Methods section for further information.

Purpose

Contact tracing is a process that is used to identify, educate, and monitor individuals who have had close contact with someone who is infected with a virus; these individuals are at a higher risk of becoming infected and sharing the virus with others. Contact tracing can help the individuals understand their risk and limit further spread of the virus. This note provides a summary of the evidence and jurisdictional experiences on contact tracing approaches to contain the COVID-19 pandemic.

*The full version of the Briefing Note including the Appendix can be accessed in the PDF file at the top of the page*

Key Findings

Analysis for Ontario

Supporting Evidence

This section summarizes the scientific evidence and jurisdictional experiences regarding contact tracing approaches during the COVID-19 epidemic. In terms of information on jurisdictional experience, most of the information presented is based on case study findings on how Germany, Iceland, Israel, Singapore, South Korea, and Taiwan contained the COVID-19 epidemic through rigorous contact tracing. Additional information on other jurisdictions was included if available.

Scientific Evidence

  • No relevant evidence-based guidelines have been identified regarding contact tracing for people who have been in contact with a person with a suspected or confirmed diagnosis of COVID-19; thus, no conclusions can be drawn.

International Scan

  • Traditional Contact Tracing Approaches: Germany, Iceland, Israel, Singapore, South Korea, and Taiwan primarily rely on traditional contact tracing approaches, in which contacts are identified through a thorough review of available data (e.g., telephone interviews with the infected individual, family, and/or physician; travel or police records; credit card transactions; closed-circuit television footage). In general, contact tracing teams within local public health units call infected individuals to communicate test results and/or inquire about any contacts that occurred in the days preceding symptom onset.
  • Digital Contact Tracing Approaches: The most commonly used digital approaches involve smartphone applications (apps) using global positioning system (e.g., Israel, Iceland) or Bluetooth (e.g., Singapore, Australia, United Kingdom) data,c as well as linked data and cloud-based technologies (e.g., South Korea, Taiwan). Other digital approaches include:
    • Quick Response (QR) Codes added to public venues to enable identification of contacts should an outbreak occur (e.g., Singapore, New Zealand).
      • For example, New Zealand’s NZ COVID Tracer voluntary app creates a digital diary of the places users visit by users scanning QR code posters that contain information about the name and location of businesses. It is meant to support manual contact tracing conducted by public health units and the National Close Contact Service.
    • Massachusetts Institute of Technology (MIT) Review’s Covid Tracing Tracker is a database that captures details (e.g., mandatory vs. voluntary, number of users and penetration rate, centralized vs. decentralized, data destruction, type of technology) of automated contact tracing efforts backed by national governments around the world.
  • Maintaining Surveillance and Capacity: Key factors that may have contributed to effective contact tracing include:
    • Mounting an early response: Many jurisdictions began implementing public health measures before the first imported case was detected (e.g., activating taskforces, initiating testing among symptomatic international travellers), which enabled them to coordinate multiple sectors of government for a proactive response.
    • Human resource capacity for contact tracing: Although manual contact tracing is the preferred approach, it is very resource-intensive and may rapidly become overwhelmed. Human resource capacity for contact tracing in most jurisdictions was achieved through redeployment and training of employees and volunteers across governmental and nongovernmental sectors (e.g., health care workers, medical students, armed forces, police)
      • The number of contact tracers range from: five per 20,000 inhabitants in Germany (as of late April 2020), 52 contact tracers in Iceland (as of late March 2020), 200+ in New Zealand (as of May 29, 2020), 240 in San Francisco (as of late April 2020), 700 in Singapore (as of late March 2020), and 1,800 teams, each with at least five members, in Wuhan, China (as of late February 2020)
  • Effectiveness: It may not be possible to directly attribute containment of the COVID-19 epidemic to any single public health measure. Nonetheless, Singapore, Iceland, Taiwan, and South Korea did not impose a national lockdown, which supports at least partial effectiveness of contact tracing approaches. For instance, Taiwan and Singapore have had success in containing the outbreak without a lockdown initially and over time. Moreover, Iceland presents compelling evidence supporting the effectiveness of rigorous contact tracing to limit further transmission, with high rates of accurate identification of imported versus community-linked COVID-19 cases and those in isolation or quarantine.
    • Bluetooth, global positioning system, and cloud-based technologies may serve as useful tools for supporting contact tracing, particularly in densely populated areas where not all contacts may be known to the infected individual.
      • However, due to privacy and usability concerns, digital contact tracing tools may best serve as supplementary measures to traditional contact tracing. This approach has been recommended by the World Health Organization.

Canadian Scan

  • The Public Health Agency of Canada developed guidance for federal/provincial/territorial public health authorities to support the management of cases and contacts of COVID-19 within their jurisdictions. It includes recommendations for frequency and type of follow-up stratified by exposure risk level (low, medium, or high)
    • For example, British Columbia (May 15, 2020) and Nova Scotia (May 22, 2020) have issued interim guidance on case and contact management for COVID-19.
  • Only one province was identified that has moved towards using a digital contact tracing approach.
    • Alberta’s ABTraceTogether is a mobile contact tracing app using Bluetooth that can be voluntarily downloaded by users to let them know if they have been exposed to or have exposed others to COVID-19. It is a tool to complement traditional manual contact tracing completed by public health officials who work at Alberta Health Services (AHS). Personal data is only stored on the user’s phone for 21 days in an encrypted format; it can only be shared with AHS contact tracers with the user’s permission
  • The Canadian firm, BlueDot, disseminates near-real-time insights on COVID-19 movements to clients, including governments, hospitals, and airlines, based on over 40 pathogen-specific datasets reflecting disease mobility and outbreak potential.

Ontario Scan

  • On April 27, 2020, the Government of Ontario released its framework document for reopening the province, echoing the need to strengthen public health capacity for rigorous testing, timely contact tracing, and case management.
    • One of the criteria being considered for determining when to ease public health measures and for ongoing monitoring of progress is that approximately 90% of new COVID-19 contacts are being reached by local public health officials within one day, with guidance and direction to contain community spread.
  • Public Health Ontario, in collaboration with the Ministry of Health and the federal government, is leading the COVID-19 Contact Tracing Initiative. To date, contact tracing is led by Ontario’s public health units, but additional capacity is required because of the rising number of cases and contacts to manage.

Methods

The COVID-19 Evidence Synthesis Network is comprised of groups specializing in evidence synthesis and knowledge translation. The group has committed to provide their expertise to provide high-quality, relevant, and timely synthesized research evidence about COVID-19 to inform decision makers as the pandemic continues. The following members of the Network provided evidence synthesis products that were used to develop this Evidence Synthesis Briefing Note:

  • Ontario Health (Cancer Care Ontario). (May 18, 2020). Personal Communication to Research, Analysis and Evaluation Branch.
  • Ontario Health (Quality). (May 18, 2020). Personal Communication to Research, Analysis and Evaluation Branch.
  • Unity Health – St. Michael’s Hospital. (May 18, 2020). Personal Communication to Research, Analysis and Evaluation Branch.

For more information, please contact the Research, Analysis and Evaluation Branch (Ministry of Health).