COVID-19 Case Investigation and Contact Tracing in New York City, June 1, 2020, to October 31, 2021

Abstract

ImportanceContact tracing is a core strategy for preventing the spread of many infectious diseases of public health concern. Better understanding of the outcomes of contact tracing for COVID-19 as well as the operational opportunities and challenges in establishing a program for a jurisdiction as large as New York City (NYC) is important for the evaluation of this strategy.ObjectiveTo describe the establishment, scaling, and maintenance of Trace, NYC’s contact tracing program, and share data on outcomes during its first 17 months.Design, Setting, and ParticipantsThis cross-sectional study included people with laboratory test–confirmed and probable COVID-19 and their contacts in NYC between June 1, 2020, and October 31, 2021. Trace launched on June 1, 2020, and had a workforce of 4147 contact tracers, with the majority of the workforce performing their jobs completely remotely. Data were analyzed in March 2022.Main Outcomes and MeasuresNumber and proportion of persons with COVID-19 and contacts on whom investigations were attempted and completed; timeliness of interviews relative to symptom onset or exposure for symptomatic cases and contacts, respectively.ResultsCase investigations were attempted for 941 035 persons. Of those, 840 922 (89.4%) were reached and 711 353 (75.6%) completed an intake interview (women and girls, 358 775 [50.4%]; 60 178 [8.5%] Asian, 110 636 [15.6%] Black, 210 489 [28.3%] Hispanic or Latino, 157 349 [22.1%] White). Interviews were attempted for 1 218 650 contacts. Of those, 904 927 (74.3%) were reached, and 590 333 (48.4%) completed intake (women and girls, 219 261 [37.2%]; 47 403 [8.0%] Asian, 98 916 [16.8%] Black, 177 600 [30.1%] Hispanic or Latino, 116 559 [19.7%] White). Completion rates were consistent over time and resistant to changes related to vaccination as well as isolation and quarantine guidance. Among symptomatic cases, median time from symptom onset to intake completion was 4.7 days; a median 1.4 contacts were identified per case. Median time from contacts’ last date of exposure to intake completion was 2.3 days. Among contacts, 30.1% were tested within 14 days of notification. Among cases, 27.8% were known to Trace as contacts. The overall expense for Trace from May 6, 2020, through October 31, 2021, was approximately $600 million.Conclusions and RelevanceDespite the complexity of developing a contact tracing program in a diverse city with a population of over 8 million people, in this case study we were able to identify 1.4 contacts per case and offer resources to safely isolate and quarantine to over 1 million cases and contacts in this study period.

Contact tracing: Characteristics of COVID-19 cases that provided contacts

“…Therefore, while contacts were not elicited from all cases, there was success in eliciting contacts from prioritized groups among individuals interviewed. The proportion of interviewed cases that provided contacts in NYS was comparable to that in NYC and fell within the range observed elsewhere [5,[8][9][10][11]. Understanding the population groups that provided contacts and those who may require targeted outreach for contact-tracing is essential at reducing the percentage of interviewed cases who report zero contacts, which was documented to be over 40% in this study.…”

“…While evidence points to success, contact elicitation from cases was a challenge. Wide variations in the percentage of cases providing contact existed and ranged from 21 percent to 87 percent [6,[8][9][10][11]. Literature identifying groups with success or challenges in contact elicitation, particularly from prioritized groups [12][13][14], is absent.…”

Scalable Strategies to Increase Efficiency and Augment Public Health Activities During Epidemic Peaks

“…However, only 11% of seed cases with completed surveys had at least one peer enroll by day 4 postdiagnosis. This represents the outer margin of the intervention window for slowing onward transmission for SARS-CoV-2,27 particularly given that most seed cases were diagnosed a few days into their infection cycles, similar to other programs,28 and that the serial interval time for SARS-CoV-2 for the majority of seed cases (enrolled during Delta and Omicron waves) may have been as short as 3 to 4 days 29. Disrupting transmission in this setting would require a combination of the Snowball Platform to distribute or make available highly accurate rapid home tests with a way to report results, combined with biometric monitoring as a second layer of targeting resources to highly infectious or even preinfectious persons.…”

Lessons learned from the launch and implementation of the COVID-19 contact tracing program in New York City: a qualitative study

“…Although T2 showed strong performance, it is not known what aspects of the program facilitated this performance, and what aspects acted as barriers to higher operational performance. Leaders of the T2 Program published a description of the case investigation and contact tracing pillar of T2 [5], but to our knowledge no studies have examined facilitators and barriers of the rapid launch and scale-up of the program. Findings from a study characterizing various US-based case investigation and contact tracing programs indicate that programs were highly contextualized and varied in terms of their structures as well as barriers and facilitators to program implementation [6].…”