A study by Columbia University Mailman School of Public Health researchers uses contract tracing data to produce a detailed to-date map of the spread of SARS-CoV-2 in New York City. They found that the city’s contact tracing program was effective and produced data that can inform neighborhood-level interventions such as vaccination and reactive restriction of business capacity.
The study is published in the journal Nature Communication.
Researchers analyzed contact tracing and testing records for 644,029 cases and their contacts in New York City during the second pandemic wave between October 1, 2020 and May 10, 2021. Data was collected by NYC Test & Trace Corps and the Department of Health and Health. Mental hygiene.
They found that it was not possible to establish chains of transmission at the individual level because more than 90% of self-reported close contacts were primarily household members and data on contacts outside the home were incomplete. Instead, researchers focused on how SARS-CoV-2 spread in communities and the effects of control measures and vaccination on its spread. They also looked at the operational performance of contact tracing.
By reconstructing chains of transmission, the authors found great heterogeneity in the number of reported close contacts and secondary infections. Transmission networks also reveal the spatial pattern of SARS-CoV-2 transmission in neighborhoods. The combination of vaccination and reactive neighborhood-based interventions likely reduced the spread of COVID-19 during the second wave.
Neighborhoods with many visitors, such as those with a high density of businesses, were associated with high levels of transmission in these areas and to other neighborhoods.
Any future isolation measures should consider frontline workers. “People working in essential businesses or emergency services may not be able to reduce their travel, while people who travel long distances to find resources may be better served by delivering or relocating resources. “, says Sen Pei, PhD, assistant professor of environmental health sciences at Columbia Mail School.
Additionally, since communities with high test positivity are typically areas of high poverty, policymakers should provide supports for isolation and quarantine (food delivery, medicine delivery, and access to places of isolation safe), add the researchers.
According to the study, the contact tracing operation in New York was highly efficient with short turnaround times. The median time between taking the sample and reporting the results to the Ministry of Health and Mental Hygiene was two days. Ninety-seven percent of index patients were called by tracers within two days of being reported to DOHMH and 68% of contacts were called on the day of reporting to the Test & Trace team. Of the contacts tested, two-thirds requested a test within a week of being notified. For traced symptomatic infections, 87% were tested after symptom onset and 13% were tested before symptom development.
In the future, contract tracing could be improved through the integration of app-based services or Bluetooth that would provide contact information beyond household members, the researchers say. However, to be effective, care must be taken to address privacy concerns.
“Contact tracing is useful information and could potentially become even more useful in the future, with COVID-19 or another infectious outbreak,” Pei says. “At the height of an outbreak, policymakers can see in real time which neighborhoods are most at risk and direct resources to prevent infections.”
Study co-authors include Jeffrey Shaman (lead author), Sasikiran Kandula, Jaime Cascante Vega, Wan Yang, Columbia Mailman School; Steffen Foerster, Corinne Thompson, Jennifer Baumgartner, Shama Desai Ahuja, Kathleen Blaney, New York City Department of Health and Mental Hygiene; Jay K. Varma, Weil Cornell Medical College; Theodore Long, NYC Health + Hospitals.
The study was supported by funding from the National Institutes of Health (AI163023), Centers for Disease Control and Prevention (U01CK000592, 75D30122C14289), National Science Foundation (DMS-2229605), Council of State and Territorial Epidemiologists ( NU38OT00297) and a gift from the Morris-Singer Foundation.