Contact tracing programs have been deployed around the world to slow the spread of COVID-19, but these programs have been unable to prevent the multiple waves of transmission and deaths that have occurred since March 2020. In a new study published in the Proceedings of the National Academy of Sciencesresearchers from the University of Texas at Austin found that a five-day delay between identifying a case and isolating contacts was the Achilles’ heel of a contact tracing program in a large American city.
Using a mathematical model to analyze data collected by the program between October 2020 and January 2021, the study concludes that shortening this timeframe from five days to just one day would prevent 26.6% more infections under certain conditions. The results can inform cities’ efforts to increase the effectiveness of contact tracing programs, including those intended to mitigate the effects of emerging threats.
The UT COVID-19 Modeling Consortium and Dell Medical School team built a model based on data from a contact tracing program, using information collected by Dell Med under the authority of Austin Public Health. They simulated a slew of strategies to increase program efficiency, including detecting a larger fraction of symptomatic cases, successfully tracing more contacts, and reducing the time it takes to isolate a contact. These three levers can significantly slow the spread of COVID-19, but the feasibility of each strategy will depend on the availability of testing, contact tracing personnel, isolation facilities, and other key resources.
The bottom line: In a burgeoning pandemic with a highly infectious virus, every day counts. In Austin, researchers estimated that the time it took to isolate a contact was three days longer in the general community than in the university community. Reducing the number of days in isolation from five to two translates to an approximately 40% reduction in new infections.
“The challenge with COVID is that people can spread the virus before they show symptoms. So the sooner we isolate potentially infected contacts, the better,” said Darlene Bhavnani, assistant professor of population health at Dell Medical School and collaborator on the consortium. “Preventing a single infection not only protects an individual, but breaks the possible chain of transmission.”
“Many COVID-19 contact tracing programs in the United States lacked the resources they needed to prevent the worst of the pandemic,” said Lauren Ancel Meyers, consortium director and professor of integrative biology and Statistics and Data Science at UT. “The answer is not to dissolve them but to strengthen them. In the perspective of COVID-19 and future pandemic threats, our study suggests that we should invest in technologies and strategies that increase the speed and success of contact tracing.
Contact tracing programs not only slow the spread, but also collect valuable information about the virus and disseminate essential health information throughout the community, Bhavnani said. “This nudge from the tracer to get tested, even if asymptomatic, along with information on where and when to get tested, can save lives.”
“Although PCR testing only takes a few hours, delays in sample submission, processing, registration and reporting have led to several delays,” said Xutong Wang, lead study author and alumnus of the Meyers Lab and UT consortium.
“Having interoperable and integrated electronic health records and public health surveillance systems could facilitate rapid reporting of test results,” Bhavnani said. “Monkeypox is yet another example of a virus where rapid testing, case notification and contact tracing can be essential for containment.”
Other authors are Zhanwei Du, formerly of Meyers Lab and now with the University of Hong Kong, Emily James of Dell Med, Spencer J. Fox of Meyers Lab and Michael Lachmann of Santa Fe Institute. Meyers is the Cooley Centennial Professor of Integrative Biology and Statistics and Data Science at UT.
This research was supported by the National Institutes of Health and the Centers for Disease Control and Prevention. Bhavnani’s effort on this project was also supported by core funds from Dell Med.