26 April 2020 – Policy Brief

SARS-CoV-2 contact tracing strategy: epidemiologic and strategic considerations

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The Government announced that a staged reduction in social distancing measures to prevent the spread of SARS-CoV-2 would begin on 27th April 2020. The reduction in transmission that has been achieved across Switzerland now needs to be maintained. A strong strategy for testing for SARS-CoV-2, contact tracing of people found to be infected, isolation of infected persons and quarantine of their contacts needs to be implemented to control the spread of infection and avoid a re-imposition of the strictest social distancing measures. Contact tracing activities need to include both classic person-based contact tracing and digital proximity tracing so that the process of identification and quarantine of contacts is quick enough to interrupt transmission. This policy brief summarises: the rationale for contact tracing and for quarantine of contacts; differences between classic person-based contact tracing and digital proximity tracing; the role of virological testing; and social and ethical considerations.

Executive summary

  • Contact tracing, followed by quarantine, is one of the key non-pharmaceutical interventions to contain the spread of infectious pathogens, including SARS-CoV-2.
  • In classic contact tracing, trained personnel interview a SARS-CoV-2 infected person, the index case, identify their contacts over a defined time period, and follow them up.
  • Digital proximity tracing is a new approach that notifies people who have been in close proximity to a SARS-CoV-2 index case, using bluetooth-enabled smartphone technology.
  • Classic person-based contact tracing and digital proximity tracing are complementary approaches that are both needed as part of a strategy to prevent and control SARS-CoV-2 because SARS-CoV-2 can be transmitted by people before they develop COVID-19 symptoms.
  • The contact tracing period for SARS-CoV-2 is from 3 days before the onset of symptoms.
  • Contacts should be quarantined for 10 days from the last possible date of exposure with an infected person.
  • Contacts could be tested by RT-PCR at the start and end of quarantine if asymptomatic, and if they develop symptoms at any time during quarantine.
  • Quarantine protocols (specifically with respect to timing and testing) need to be continually adjusted to newly emerging scientific evidence.
  • Protectionand assistance for people in quarantine need to be assured (including covering costs of testing) in order to achieve strong popular support and high compliance.
  • External accommodation, with medical supervision, needs to be available for contacts who live in a household with vulnerable people, or who cannot maintain quarantine in their own home.

Date of request: 20/4/2020
Date of response: 26/4/2020

In response to request from: Krisenstab

Comment on planned updates: updates planned

Expert groups and individuals involved: Digital epidemiology, PH, D&T, ELSI

Contact persons:

As the Swiss National COVID-19 Science Task Force has been disbanded as of 31 March 2022, no further epidemiological assessments, scientific updates or policy briefs will be published in the future. All previous publications, pages and information of the Science Task Force remain available on this website.