Study examines contract tracing speed effectiveness

Recently released study findings published in The Lancet Public Health journal has determined contact tracing speed strategies to be essential to slowing COVID-19 transmission.

Contact tracing involves tracking down all of the people who have been in contact with an infected individual so they can be isolated to prevent further spread of the virus.

Officials said the study was executed by Utrecht University, Universidade de Lisboa and University of Liverpool researchers and funded by ZonMw, Fundação para a Ciência e a Tecnologia and EU Horizon 2020 RECOVER.

If testing is delayed by three days or more after a person develops symptoms, per scientists, even the most efficient contact tracing strategy would not be able to reduce transmission advancement.

“This study reinforces findings from other modelling studies, showing that contact tracing can be an effective intervention to prevent spread of the SARS-CoV-2 virus, but only if the proportion of contacts traced is high and the process is fast,” Professor Mirjam Kretzschmar, one of the lead authors of the study, from the University of Utrecht, the Netherlands, said. “Our study builds on this to show, in detail, what role each step in the process plays in making this approach successful. This will help policymakers understand where best to prioritise resources to maximise the chances of success.”

Researchers said mobile apps can speed up the process of tracking down people who are potentially infected. Still, if testing is delayed by three days or more, even those technologies cannot stop virus transmission.

The scope of work used a mathematical model reflecting various steps and delays in the contact tracing process – enabling researchers to quantify how delays affect the fraction of onward transmission cases preventable for each diagnosed person.