Contact tracing data sheds light on COVID-19 spread in New York City

A study led by researchers at Columbia University Mailman School of Public Health uses contract tracing data to produce a detailed map to date of SARS-CoV-2 spread in New York City. They found that the city’s contact tracing program was efficient and produced data that can inform neighborhood-level interventions like vaccination and reactive restriction on business capacity.

The study is published in the journal Nature Communications.

The 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 the NYC Test & Trace Corps and the Department of Health and Mental Hygiene.

They found it was not possible to establish transmission chains at the individual level because more than 90 percent of self-reported close contacts were predominately household members and data on contacts outside home was incomplete. Instead, the researchers focused on how SARS-CoV-2 spread across communities and what the effects of control measures and vaccination on its spread. They also examined the operational performance of contact tracing.

By reconstructing transmission chains, the authors found large heterogeneity in the number of reported close contacts and secondary infections. The transmission networks also reveal the spatial pattern of SARS-CoV-2 transmission across 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 those with a high density of businesses, were associated with elevated transmission levels within those areas and to other neighborhoods.

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