EVALUATION of the COVID-19 CONTACT TRACING PROGRAM in KING COUNTY, WA, USA

ABSTRACT

Background: Case investigation and contact tracing (CI/CT) is a key component of the response to COVID-19. CI/CT seeks to ensure that people exposed to SARS-CoV2 learn of their exposure and that infected persons and their contacts adhere to isolation and quarantine (I/Q) guidance. CI/CT programs also have the potential to address pandemic-related health inequities through the provision of support services. We evaluated the Public Health-Seattle & King County (PHSKC) CI/CT program, including its reach, timeliness, and case-reported impact on I&Q adherence. Methods: The PHSKC CI/CT case interview assessed case demographics, recently visited places, contacts, and service needs. In March 2021, a random sample of cases completed an End of I&Q Survey to assess their adherence to I&Q guidance and opinions of CI/CT. We calculated descriptive statistics to evaluate survey and programmatic data collected between July 2020 and June 2021. Results: The PHSKC CI/CT team interviewed 42,018 cases (81% of cases contacted) a mean of 6.1 days after symptom onset, and 3.4 days after SARS-CoV2 testing. Cases disclosed the names and addresses of 10,650 worksites (mean= 0.8/interview) and 11,269 other recently visited locations (mean= 0.5/interview), and provided contact information for 61,969 household members (mean=2.7/interview) and 8,753 non-household contacts (mean= 0.3/interview). The CI/CT team helped arrange COVID-19 testing for 5,660 contacts from 3,104 households, facilitated grocery delivery for 7,257 households, and referred 9,127 households for financial assistance. End of I&Q Survey participants (n=304, 54% of sampled) reported self-notifying an average of 4 non-household contacts and 69% agreed that the information and referrals provided by the CI/CT team helped them stay in isolation. Conclusion: CI/CT reached many persons with COVID-19 and their household contacts and identified thousands of possible exposure venues. The intervention's effectiveness was likely limited by the inability to interview cases during their period of peak infectiousness and cases' reluctance to name non-household contacts, though cases notified many non-household contacts themselves. CI/CT was effective in linking people to testing, food, and financial assistance, and most cases reported that the intervention helped them isolate. These findings provide evidence that CI/CT can help mitigate the impact of COVID-19 on disproportionately impacted communities through the promotion of I&Q guidance and provision of support services.