Contact tracing for COVID-19

Countries should follow the latest ECDC contact tracing guidance.

To find out more, please take the e-learning course ‘Contact tracing in the context of COVID-19 response’.

Contact tracing in relation to Omicron

Contact tracing can help prevent Omicron from being established in the community.

The ECDC contact tracing guidance sets out specific enhanced contact tracing measures such as backward contact tracing and stricter management for contacts of cases suspected to be infected with a Variant Of Concern. These are set out in the section ‘Options for enhanced contact tracing’ starting on page 10.

ECDC recommends that such enhanced measures are considered for possible, probable or confirmed cases of COVID that are suspected to be infected with Omicron (e.g. as a result of laboratory pre-screening such as S-gene deletion, or any case with an epidemiological link). This means, for example, that for a symptomatic person with an epidemiological link to an affected area or to a known case, contact tracing should start even before the COVID-19 test result is returned.

With regards to contact tracing of passengers on aircrafts, ECDC has developed specific recommendations and these are available in the third update of the ECDC contact tracing guidance. However, this guidance was developed prior to the widespread emergence of variants with high transmissibility. A more precautionary approach in relation to the classification of contacts on planes could therefore be considered in relation to the current situation with the Omicron variant. This approach could be to consider all passengers and cabin crew members that have travelled on a flight with a confirmed or probable case as having a high-risk exposure and that these fellow passengers are managed as contacts in accordance with the guidance on contact tracing noted above.

When contact tracing investigations identify contacts or a potential source in another country, public health authorities should collaborate across borders and exchange data in a secure way (through, for example, the selective exchange messaging function of the Early Warning and Response System (EWRS) of the European Union or share data using the European Digital Passenger Locator Form).

As the situation is rapidly evolving, please refer to the latest ECDC Threat Assessment Brief for the most up-to-date information.

Principles of contact tracing

The aim of identifying and managing the contacts of COVID-19 cases is to support early diagnosis and interrupt onward transmission by rapidly identifying and managing any secondary cases that may arise following transmission from primary cases. This is achieved by:

• promptly identifying the contacts of a COVID-19 case;
• providing contacts with information on self-quarantine, proper hand hygiene and respiratory etiquette, and advice on what to do if they develop symptoms;
• testing all contacts who have had high-risk exposure to COVID-19 cases, whether or not they are symptomatic, as soon as possible after they have been identified, to allow for further contact tracing;
• testing all contacts who have had low-risk exposure to COVID-19 cases in settings where transmission is likely and/or the population is vulnerable to severe COVID-19;
• testing all contacts that become symptomatic.

Contact tracing is a key tool for breaking transmission chains. For countries with high transmission, contact tracing will complement other measures, such as physical distancing, and help reduce transmission. For countries with lower levels of transmission, contact tracing is the key to outbreak management and control of transmission.

For contact tracing to be effective it needs to be prompt. This includes testing cases as soon as possible after symptom onset – which requires a high level of public awareness and easy access to testing. Test turnaround time should be minimised, and contacts traced as soon as possible after a positive result. While awaiting the results of their test, those who are symptomatic can be encouraged to inform their close contacts and suggest to them that they adhere to physical distancing measures until the result is known.

Additional information on different settings can be found below.

Monitoring

ECDC and WHO encourage countries to monitor the effectiveness of their contact tracing operations in order to identify where coverage or timeliness needs to be improved (See ECDC’s publication Monitoring and evaluation framework for COVID-19 response activities in the EU/EEA and the UK). To learn more about the transmissibility and characteristics of VOCs, countries are encouraged to collect and analyse contact tracing data from these cases and to share findings with ECDC, WHO and other EU/EEA countries.

Data collection

This reporting protocol describes the collection of data regarding contact tracing. The data collection aims to help assess the effectiveness and efficiency of contact tracing operations, to provide information on transmission of SARS-CoV-2, and to provide contextual information on the progression of the pandemic to tailor response measures.

Mobile apps

Countries using mobile apps for contact tracing are also encouraged to refer to ECDC’s guidance on mobile apps in support of contact tracing and to monitor their effectiveness using the joint WHO-ECDC indicator framework.

With regard to VOCs, countries are encouraged to monitor the number of contacts testing positive of those notified, or apply similar measures in order to understand whether the parameter settings need calibration – e.g. due to a more transmissible variant. ECDC’s guidance on mobile apps has further details on evaluating and calibrating settings.

Passenger Locator Forms

On 27 May 2021, the European Commission published the Implementing Decision 2021/858 outlining the function of the digital Passenger Locator Form (dPLF) in the EU/EEA.

Additional documents on contact tracing, including those related to special settings or populations