Key Points
Question
What were the outcomes of the COVID-19 contact tracing program in New York City?
Findings
In this cross-sectional study, a workforce of 4147 contact tracers attempted case investigations on 941 035 persons and contact interviews on 1 218 650 persons from June 1, 2020, to October 31, 2021. Overall expense from May 6, 2020, to October 31, 2021, was approximately $600 million.
Meaning
These results suggest that a large program can be rapidly developed, operationalized, and subsequently maintained.
This cross-sectional study examines the scope and results of a COVID-19 contact tracing program in New York City
Abstract
Importance
Contact 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.
Objective
To 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 Participants
This 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 Measures
Number 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.
Results
Case 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 Relevance
Despite 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.
Introduction
New York City (NYC), the largest city in the US, has been heavily affected by COVID-19, with 1 947 225 confirmed cases and 39 910 confirmed and probable deaths as of March 15, 2022.1 NYC launched a citywide contact tracing operation as part of a new program called the Test & Trace Corps on June 1, 2020, when the 7-day daily average of new confirmed cases was 620. The corps is operated by NYC’s public health care delivery agency, NYC Health + Hospitals, which provides clinical, laboratory, and social services. Test & Trace was supported by the NYC Department of Health and Mental Hygiene (DOHMH).2
Contact tracing is a core strategy for preventing the spread of many infectious diseases of public health concern. For COVID-19, it involves rapidly identifying persons with asymptomatic or symptomatic COVID-19 and their contacts and implementing isolation and quarantine, respectively.3 A comprehensive COVID-19 contact tracing program requires multiple services to function in concert to ensure equitable access to testing, health care, and resources to support separation.4,5 In this study we describe the establishment, scaling and maintenance of Trace, NYC’s contact tracing program, and share data on outcomes during its first 17 months of operation (from June 1, 2020, October 31, 2021).
Methods
Case Reporting
During the study period, entities performing laboratory-based or point-of-care SARS-CoV-2 testing for New York State (NYS) residents were required by law to report positive and negative results to the NYS Department of Health (DOH). NYS DOH then forwarded results for all NYC residents to NYC DOHMH in near real time.6 DOHMH therefore has a nearly complete registry of all NYC residents diagnosed with COVID-19 whose tests were ordered by a clinician.5 This study was considered exempt from review and informed consent requirement because of a nonresearch determination from the DOHMH institutional review board. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guidelines for cross-sectional studies.
Once daily, DOHMH exported records of probable (ie, positive antigen test) and confirmed (positive molecular test) cases to Trace for upload into a cloud-based customer relationship management software integrated with a telephony system (Salesforce, Inc).7,8 Data on all NYC residents with COVID-19 (regardless of symptom status) were sent to Trace, except for data on persons living in congregate settings based on residential address; contact tracing for these cases was performed by DOHMH.
Case Management
Once uploaded to Salesforce, case records were assigned to contact tracers for investigation. Case investigations were performed on persons with probable or confirmed COVID-19 and on contacts with COVID-19 symptoms even if the contact had no COVID-19 test result available (referred to as symptomatic contacts) by case investigators (937 case investigators at peak).9
Case investigators provided education, assessed symptoms, elicited close contacts (ie, persons within 6 feet of the person undergoing case investigation while potentially infectious for 10 or more cumulative minutes), identified locations the person visited while infectious, evaluated need for supportive services, and advised on duration of isolation.10 These persons were advised to isolate throughout the duration of their infectious period, beginning 2 days prior through 10 days after date of symptom onset (or date of specimen collection if asymptomatic); before October 1, 2020, 14 days was used instead of 10 days per NYSDOH guidance.11,12 After completion of case investigations, persons with COVID-19 and symptomatic contacts were monitored during their infectious period either via phone call or short message service (SMS).
Contact Management
Contacts named by persons undergoing a case investigation or an investigation performed at the facility level (eg, a school) were assigned to separate staff (referred to as monitors; 2670 monitors at peak) who performed intake interviews and completed daily case and contact monitoring. During intake, monitors provided education, assessed symptoms, advised on testing, evaluated need for supportive services, and informed contacts when to end quarantine.
Contacts were advised to quarantine for 14 days following their last exposure from June 1 to December 29, 2020, until NYS DOH updated guidance to recommend 10 days of quarantine.13,14 On March 11, 2021, Trace stopped recommending quarantine for contacts who were vaccinated per NYS DOH guidance; to help advise on quarantine, Trace began verifying vaccination status through an integration of DOHMH’s Citywide Immunization Registry with Salesforce. In September 2021, Trace began allowing contacts to test out of quarantine.15 After completion of intake, contacts who met criteria for quarantine were monitored via phone call or SMS (eMethods in the Supplement).
Finding Hard-to-Reach Clients
Clients (people with COVID-19 or contacts) who could not be reached because of insufficient contact information or failure to respond to at least 3 outreach attempts were assigned to a team of information gatherers. Information gatherers (74 at peak) used Regional Health Information Organizations databases and CLEAR, a commercial application, to identify additional contact information that could be used to reach clients.16,17 For persons with COVID-19, gatherers also performed outreach to clinicians to obtain missing contact information.
Clients were referred to a team of community engagement specialists if information gatherers could find no additional contact information.18 If an address was available, an engagement specialist (540 at peak) performed a home visit. If an address was not available, the client’s record was marked unable to locate and closed. Management of contact tracing was conducted differently in indoor group settings (eg, schools, workplaces), which included investigations conducted at the facility level and interjurisdictional activities (eMethods in the Supplement).
Supportive Services for Clients
All clients were offered supportive services to safely separate from others throughout the duration of isolation and quarantine either at home or at a hotel at no direct expense to them. Clients were offered food and medication delivery, information about NYS paid sick leave, and other resources. Clients were offered care packages including masks, hand sanitizer, and a thermometer. Persons with COVID-19 also received pulse oximeters. Contacts were offered at-home specimen collection or test kits as available.
Workforce
All staff completed courses on COVID-19 in addition to role-specific exercises, Salesforce orientation, and trainings on privacy and confidentiality.19 Staff also completed training in health equity, trauma-informed care, and implicit bias. Most trainings were conducted remotely. The community engagement team received additional in-person trainings not required of remote staff (eg, use of personal protective equipment and safety). All case investigators and community engagement specialists lived in NYC, and more than 50% were hired from communities hardest hit by COVID-19; together, these staff spoke over 40 languages.
Trace launched June 1, 2020, and at its peak in August 2020 had a workforce of 3990 contact tracers, with 4147 contact tracers cumulatively hired throughout the course of the program. Most staff (87%) performed their jobs completely remotely.
Statistical Analysis
All analyses were performed in R version 3.5.2 (R Project for Statistical Computing). Data were analyzed in March 2022.
Results
From June 1, 2020, to October 31, 2021, 941 035 case investigations were attempted on persons with probable and confirmed COVID-19 (797 998 [84.8%]) and symptomatic contacts (143 037 [15.2%]). Of these, 840 922 (89.4%) were reached and 711 379 (75.6%) completed case investigations (Figure 1). Of those who completed case investigations, 358 775 individuals (50.4%) were women or girls; by race and ethnicity, 60 178 (8.5%) identified as Asian, 110 636 (15.6%) as Black, 210 489 (28.3%) as Hispanic or Latino, and 157 349 (22.1%) as White (Table 1). During the same period, 1 218 650 intake interviews were attempted for contacts. Of these, 904 927 (74.3%) were reached, and 590 364 (48.4%) completed intake (Figure 2). Of the contacts who completed intake, 219 261 individuals (37.2%) were women or girls; 47 403 (8.0%) identified as Asian, 98 916 (16.8%) as Black, 177 600 (30.1%) as Hispanic or Latino, and 116 559 (19.7%) as White. Attempts were made to reach 881 080 (93.6%) cases and 1 143 389 (93.8%) contacts within 24 hours of referral to Trace. Completion rates were consistent over time and resistant to changes related to vaccination and isolation and quarantine guidance. Among 711 379 laboratory-positive cases, 598 232 (84.1%) had 1 or more symptoms during their infectious period. Among contacts, 168 900 (28.6%) reported symptoms during their monitoring period (Table 2).
Figure 1. COVID-19 Cases Investigated in New York City Between June 1, 2020, and October 31, 2021.
aLaboratory confirmed and probable cases and symptomatic contacts
Table 1. Attributes Reported by Persons With COVID-19 and Their Contacts in New York City, June 1, 2020, to October 31, 2021.
| Characteristic | Cases, No. (%) (n = 711 379)a | Contacts, No. (%) (n = 590 364)b |
|---|---|---|
| Borough | ||
| Bronx | 130 703 (18.4) | 102 197 (17.3) |
| Brooklyn | 209 421 (29.4) | 150 542 (25.5) |
| Manhattan | 102 472 (14.4) | 62 131 (10.5) |
| Queens | 198 192 (27.9) | 146 277 (24.8) |
| Staten Island | 58 846 (8.3) | 45 096 (7.6) |
| Unknown | 11 745 (1.7) | 84 121 (14.2) |
| Gender | ||
| Female | 358 775 (50.4) | 219 361 (37.2) |
| Male | 297 237 (41.8) | 168 902 (28.6) |
| Transgender, nonbinary, genderqueer, or not listed | 2124 (0.3) | 1171 (0.2) |
| Unknown | 53 243 (7.5) | 200 930 (34.0) |
| Sexual orientation | ||
| Bisexual | 5642 (0.8) | 3278 (0.6) |
| Gay or lesbian | 10 626 (1.5) | 5022 (0.9) |
| Queer | 1684 (0.2) | 1061 (0.2) |
| Questioning | 232 (<0.1) | 163 (<0.1) |
| Straight or heterosexual | 346 809 (48.8) | 227 303 (38.5) |
| Not listed | 885 (0.1) | 530 (0.1) |
| Unknown | 345 501 (48.6) | 353 007 (59.8) |
| Racec | ||
| Asian | 60 178 (8.5) | 47 403 (8.0) |
| Black | 110 636 (15.6) | 98 916 (16.8) |
| Native Hawaiian, Pacific Islander, Native American, or Alaskan Native | 3900 (0.5) | 3881 (0.7) |
| White | 157 349 (22.1) | 116 559 (19.7) |
| Multiracial | 8946 (1.3) | 9207 (1.6) |
| Did not identify with any race provided | 76 172 (10.7) | 68 946 (11.7) |
| Unknown | 294 198 (41.4) | 245 452 (41.6) |
| Ethnicity | ||
| Hispanic or Latino | 201 489 (28.3) | 177 600 (30.1) |
| Not Hispanic or Latino | 290 773 (40.9) | 229 966 (39.0) |
| Unknown | 219 117 (30.8) | 182 798 (31.0) |
| Age group, y | ||
| 0-4 | 26 871 (3.8) | 46 359 (7.9) |
| 5-12 | 37 932 (5.3) | 60 502 (10.2) |
| 13-17 | 79 238 (11.1) | 50 944 (8.6) |
| 18-24 | 153 772 (21.6) | 81 140 (13.7) |
| 25-34 | 115 501 (16.2) | 69 279 (11.7) |
| 35-44 | 94 742 (13.3) | 60 032 (10.2) |
| 45-54 | 58 554 (8.2) | 138 616 (23.5) |
| 55-64 | 79 312 (11.1) | 45 072 (7.6) |
| 65-74 | 42 210 (5.9) | 20 332 (3.4) |
| ≥75 | 22 931 (3.2) | 9706 (1.6) |
| Unknown | 316 (<0.1) | 8382 (1.4) |
| Disability | ||
| Any | 53 119 (7.5) | 39 264 (6.7) |
| Difficulty concentrating, remembering, or deciding | 20 880 (4.1) | 18 146 (4.3) |
| Difficulty dressing | 10 908 (2.2) | 7529 (1.8) |
| Difficulty running errands | 15 597 (3.1) | 11 290 (2.8) |
| Difficulty hearing | 4512 (0.7) | 3025 (0.6) |
| Difficulty seeing | 17 259 (3.4) | 12 969 (3.1) |
| Difficulty walking or climbing stairs | 27 253 (5.4) | 16 347 (3.9) |
| Any comorbidity | ||
| Any | 238 470 (33.5) | 154 271 (26.1) |
| Diabetes | 47 302 (7.5) | 25 627 (4.9) |
| Myocardial infarction | 18 572 (2.9) | 9177 (1.7) |
| Hypertension | 90 688 (14.3) | 49 732 (9.5) |
| Immunocompromised | 39 681 (6.3) | 21 231 (4.0) |
| Kidney disease | 6150 (1.0) | 3049 (0.6) |
| Liver disease | 5605 (0.9) | 4141 (0.8) |
| Lung disease | 61 886 (9.8) | 46 825 (8.9) |
| Organ transplant | 1783 (0.3) | 961 (0.2) |
| Overweight | 104 028 (16.5) | 70 487 (13.4) |
| Sickle cell disease | 3570 (0.6) | 2830 (0.5) |
| Smoke or vape | 54 398 (8.8) | 33 148 (6.6) |
| Work sector | ||
| Arts, design, entertainment, sports, and media | 2141 (0.3) | 4309 (0.7) |
| Building and grounds cleaning and maintenance | 2361 (0.3) | 5413 (0.9) |
| Construction and extraction | 3353 (0.5) | 7412 (1.3) |
| Educational instruction and library | 8557 (1.2) | 35 445 (6.0) |
| Emergency response services | 639 (0.1) | 1215 (0.2) |
| Food preparation and serving related | 3889 (0.5) | 9603 (1.6) |
| Health care practitioner or other technical health care | 3612 (0.5) | 7009 (1.2) |
| Health care support | 7944 (1.1) | 17 514 (3.0) |
| Management or business and financial operations | 4333 (0.6) | 8176 (1.4) |
| Office and administrative support | 5550 (0.8) | 11 787 (2.0) |
| Personal care and service | 2247 (0.3) | 5391 (0.9) |
| Retail salesperson | 3103 (0.4) | 7140 (1.2) |
| Sales or related, other than retail | 1708 (0.2) | 3411 (0.6) |
| Transportation | 2873 (0.4) | 6681 (1.1) |
| Other | 13 574 (1.9) | 29 655 (5.0) |
| Unknown | 645 495 (90.7) | 430 203 (72.9) |
Includes laboratory test confirmed and probable cases and symptomatic contacts.
Includes symptomatic and asymptomatic contacts.
Listed categories for race include South Asian in Asian, African American and Afro-Caribbean in Black.
Figure 2. COVID-19 Contacts Identified in New York City Between June 1, 2020, and October 31, 2021a.
aIndividuals within 6 feet of a person with COVID-19 while infectious for over 10 cumulative minutes.
Table 2. Symptoms Reported by Persons With COVID-19 and Their Contacts in New York City, June 1, 2020, to October 31, 2021.
| Characteristic | Cases, No. (%) (n = 711 379)a | Contacts, No. (%) (n = 590 364)b |
|---|---|---|
| Symptomatic at any time during infectious or incubation period | ||
| Any | 598 232 (84.1) | 168 900 (28.6) |
| Chest pain | 84 494 (11.9) | 19 104 (3.2) |
| Chills | 231 178 (32.5) | 48 254 (8.2) |
| Congestion | 326 284 (45.9) | 79 646 (13.5) |
| Cough | 365 389 (51.4) | 88 606 (15.0) |
| Diarrhea | 150 490 (21.2) | 33 818 (5.7) |
| Fatigue | 308 635 (43.4 | 65 706 (11.1) |
| Fever | 245 531 (34.5) | 53 521 (9.1) |
| Headache | 334 679 (47.0) | 82 917 (14.0) |
| Muscle ache | 287 312 (40.4) | 62 996 (10.7) |
| Loss of smell or taste | 286 195 (40.2) | 54 072 (9.2) |
| Shortness of breath | 107 284 (15.1) | 22 432 (3.8) |
| Sore throat | 218 776 (30.8) | 57 676 (9.8) |
| Vomiting | 115 145 (16.2) | 26 660 (4.5) |
Includes laboratory test confirmed cases and symptomatic contacts.
Includes symptomatic and asymptomatic contacts (symptomatic contacts were counted both as case and contact to demonstrate operational need to complete case investigation and contact intake).
Of cases and symptomatic contacts who completed case investigation, 421 544 (59.3%) provided names of contacts; a median of 1.4 contacts were identified per case. Of contacts, 30.1% were tested within 14 days of notification by Trace. Among all cases, 27.8% were known to Trace as contacts.
Among symptomatic laboratory tested positive cases, the median number of days from symptom onset to testing was 2.0 days, from testing to test result 1.0 day, from specimen result to upload to Salesforce 1.0 day, from upload to first call attempt 0.6 days, and from first call attempt to completed intake 0.1 days, for a total median time of 4.7 days from symptom onset to case investigation completion (Figure 3A). Among contacts, the median number of days from date of last exposure to date of elicitation was 2.0 days, from elicitation to first call attempt was 0.2 days, and from first call attempt to intake completion was 0.1 days, for a total median time of 2.3 days from last exposure to intake completion (Figure 3B).
Figure 3. COVID-19 Case Investigation and Contact Intake Timeliness Metrics in New York City Between June 1, 2020, and October 31, 2021.
A total 88 952 of 941 034 persons with COVID-19 (9.5%) and 65 826 of 1 218 647 contacts (5.4%) utilized at least 1 of the supportive services offered to them. The most requested resource for both persons with COVID-19 and contacts was food (32.8% of cases and 33.2% of contacts). Of all monitoring interactions, 97.7% of persons with COVID-19 and 96.1% of contacts reported compliance to isolation and quarantine, respectively. The overall expense for Trace from planning (beginning on May 6, 2020) through October 31, 2021, was approximately $600 000 000.
Discussion
Contact tracing is an important tool to control the spread of many infectious diseases of public health concern. A workforce of over 4000 staff was established to conduct COVID-19 contact tracing in NYC for over 1 million cases and contacts in the first 17 months of Trace. While the effectiveness of contact tracing in preventing secondary transmission of SARS-CoV-2 at a population level has been questioned given several factors, including the lack of access to testing early in the pandemic, transmission characteristics of SARS-CoV-2, and widespread level of community transmission, data from modeling studies suggest that contact tracing has been effective in reducing community transmission by as much as 21%.3 Furthermore, our experience suggests that the program was executed with relative operational success in NYC.20,21,22 For example, we completed case investigations on over 75% of cases and symptomatic contacts compared with 59% of confirmed cases in a cross-sectional study of contact tracing in multiple US jurisdictions. Furthermore, nearly 60% of NYC cases and symptomatic contacts named contacts, compared with 33% of cases in the same study.23
Timeliness is key to the success of any contact tracing operation. Trace attempted to reach all cases and contacts within 1 day of notification. Keeping up with the massive volume of new cases and contacts was made possible by maintaining a large workforce that exceeded national recommendations of 30 contact tracers per 100 000 population as well as utilizing an integrated database-telephone system.24,25 The most significant factors that affected the timeliness of contact tracing were often beyond Trace’s immediate control, such as lags between symptom onset and getting tested and delays between getting tested and result generation. Equitable, widespread access to rapid diagnostics and efficient laboratory systems are crucial to controlling health emergencies such as COVID-19. Further real-time transmission of data at every step where possible will improve timeliness.
A key goal of Trace was to embed health equity in all aspects of program implementation. Scripting for case and contact interviews, specifically demographic questions, was based on language developed by DOHMH with the goal of capturing the public health needs of different communities.26,27 We implemented tailored contact tracing practices based on feedback from community leaders, such as allowing for monitoring pauses during days of religious observance, to best serve diverse communities. Furthermore, we set up a community advisory board composed of multi-sectoral partners to give feedback on Test & Trace operations. Recommendations by board members impacted how Trace adjusted scripts, assessed disability status, and conducted trainings.28 Finally, from the program’s inception, we chose to make compliance with contact tracing voluntary, even though we had authority to issue legal isolation and quarantine orders. This approach put individual autonomy first, which is a key equity tenet given that some communities may be less engaged with government due to a history of racism experienced by these communities.
The program evolved based on accrued experience and the needs at hand. For example, on October 2, 2020, we integrated use of a smart phone–based application alongside our conventional contact tracing operation that allowed for anonymous notifications of exposures.29 To address public concerns about fraudulent callers posing as contact tracers, we implemented a multifactor authentication system that allowed for tracer validation.30 We were constrained by a data system that was not as flexible as always needed and technological updates were limited due to the complexities of the logic of the decision-support programmed into the software and competing priorities of staff. Additionally, rolling out technical changes and guidance updates to a staff of over 4000 was time consuming, especially given the pace of policy changes happening at federal and local levels. The physical and mental toll on the workforce during a lengthy public health crisis was significant. Efforts were made to address this, including holding feedback sessions, sharing resources on mental health services, and encouraging staff to take time off as needed.31 Drawing from contact tracers, NYC established a public health corps of community health workers to help patients navigate the health care system.
Limitations
There were several limitations to our operation and this analysis. First, persons with COVID-19 who were never tested or who were diagnosed only via at-home test kits were not reported to DOHMH and therefore were not referred to Trace. Additionally, respiratory viruses, by nature of their high infectivity, pose a challenge to contact tracing because spread within and across social and geographic networks can be rapid. Asymptomatic and presymptomatic spread further undermined contact tracing efficacy.32 Third, there were significant challenges to data sharing between 2 large government agencies and subsequent matching and deduplication of records. Record deduplication is a source of inaccuracies in estimating the number of unique persons exposed and infected. Next, the elicitation of 1.4 contacts per case, although higher than other jurisdictions, should be considered in the context of NYC, where it is reasonable to expect more than 1.4 contacts per case given the city’s size and density.19,33
Conclusions
Our study of the contact tracing program in NYC shows how a massive program can be established in a short timespan and adapted to reflect changes to national and local guidance. Trace was able to complete case investigations on nearly half of all cases within 24 hours of referral and was able to offer over 1 million cases and contacts access to resources to support isolation and quarantine during this period. While vaccination has now become the primary method for preventing COVID-19, contract tracing can be a tool for interrupting transmission and preventing hospitalization and death in some vulnerable populations, especially given global limitations on vaccine distribution and uptake, the possibility that immunity is neither durable nor complete and the emergence of novel strains.3,34 The overall effectiveness and sustainability of contact tracing as a public health control measure during a pandemic must be weighed against other available measures and resource considerations.
eMethods.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Citations
- New York City Health and Hospitals . Test and Trace Corps. Accessed February 15, 2021. https://www.nychealthandhospitals.org/test-and-trace/
- New York City Department of Health and Mental Hygiene . Health Alert #37: All Point-of-Care COVID-19 Test Results Must be Reported Electronically. Accessed February 18, 2022. https://www1.nyc.gov/assets/doh/downloads/pdf/han/advisory/2020/covid-19-point-of-care-test-results.pdf
Supplementary Materials
eMethods.