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’.

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.

Contact tracing related to variants of concern (VOC)

ECDC’s rapid risk assessment contains regularly updated information and each risk assessment has a section on contact tracing. The latest risk assessment is available here.

Where a case is suspected to be infected with a VOC, contact tracing can help prevent the establishment of the VOC in the country. It can also be used to investigate the source of infection of a newly identified case – known as ‘backward contact tracing’. This can also enable the identification of further cases linked to the source of infection. Further contact tracing can then take place in connection with these additional cases.

For cases suspected to be infected with a VOC (e.g. as a result of laboratory pre-screening or an epidemiological link) enhanced contact tracing measures can be considered. These enhanced measures are outlined in ECDC’s risk assessment Risk related to the spread of new SARS-CoV-2 variants of concern in the EU/EEA – first update.

Countries using mobile applications to support contact tracing 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 detail on evaluating and calibrating settings.

Contact tracing for vaccinated individuals

Interim guidance on contact tracing recommendations for vaccinated individuals can be found here.

As outlined in the interim guidance above, vaccinated contacts who have been exposed to a confirmed case should continue to be managed in accordance with existing ECDC guidance. However, health authorities may consider undertaking a risk assessment on a case-by-case basis and subsequently classifying certain fully-vaccinated individuals as low-risk contacts. When making an assessment, factors that need to be taken into consideration include the local epidemiological situation in terms of circulating variants; the type of vaccine received; the age of the contact or the risk of onward transmission to vulnerable persons by the contact.

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.

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