Completeness and timeliness of a contact tracing intervention during the coronavirus 2019 (COVID-19) pandemic: an outcome evaluation of the California Contact Tracing Support Initiative

Background and Aims Case investigation and contact tracing were among the principal strategies implemented for disease control prior to the introduction of coronavirus disease 2019 (COVID-19) vaccines in late 2020. This study aimed to evaluate outcomes of the California Contact Tracing Support Initiative (CCTSI), a program that supported COVID-19 case investigation and contact tracing activities in California between December 2020 and July 2021. Methods CCTSI conducted phone-based COVID-19 case investigations among members of Kaiser Permanente (KP) and notified their close contacts. Using de-identified secondary individual-level data from these activities, we performed descriptive analysis of program outcomes in two California counties: Fresno and San Bernardino. Completeness and timeliness were assessed as indicators of the quality of case investigation and contact notification. Referrals for wrap-around support services were analyzed to understand the program implications. To provide contextual depth and complement the quantitative findings, we conducted qualitative interviews with 47 program staff. A thematic analysis approach was used for qualitative data analysis. Results Completeness of case investigation and contact notification varied across counties. In Fresno County, 64% of assigned COVID-19 cases (2,722 of 4,279) were successfully interviewed, and 63% of assigned contacts (418 of 660) were notified. In San Bernardino County, 52% of cases (1,743 of 3,352) were interviewed, while 79% of contacts (155 of 196) were notified. Unrecognized caller identification (ID) issues were perceived as a key barrier to achieving high completeness, as many cases did not answer calls or declined participation because they were unable to verify that caller was affiliated with KP. Regarding timeliness, 49% (2,105) of case investigation in Fresno and 48% (1,621) in San Bernardino were conducted within 48 hours of receiving test results. Regarding notification, 83% of contacts in Fresno (n = 348) and 82% of contacts in San Bernardino were notified within 48 hours of contact elicitation (n = 127). Qualitative findings suggested that timely case investigation was facilitated by the rapid receipt of test results in the early program period. Although data were limited for evaluating wrap-around services, qualitative findings highlighted their value, particularly for individuals with unmet resource needs. Conclusions Investigation completeness was moderate to high, and timeliness was generally achieved within 48 hours; however, relatively few contacts were elicited per case. The evaluation highlights common challenges that require careful consideration in future contact tracing efforts, including establishing trust with beneficiaries, integrating healthcare testing and practice with public health, and designing databases to facilitate performance monitoring.