The influence of case factors and system factors on the timeliness of testing and contact tracing for COVID-19 in The Netherlands

Source and contact tracing (SCT) is essential to control the transmission of SARS-CoV-2, and the timeliness of SCT is crucial. As little is known about its real-world effectiveness, we investigated the timeliness of SCT in the Netherlands and its determinants. We used routine COVID-19 SCT data from all individuals who tested positive for SARS-CoV-2 at nine Dutch public health services between 1 June 2020 and 28 February 2021 (N = 384 591). We calculated median time intervals between SCT stages. We used multilevel logistic regression to study associations between case factors and system factors, and total SCT delay (symptom onset to SCT initiation >3 days), patient delay (symptom onset to making test appointment >1 day), and response delay (making test appointment to SCT initiation >2 days). The median total SCT interval time was 3 days (interquartile range 2-5). Older age and being a migrant had higher odds of delay; working in health care or education had lower odds of delay. A higher caseload and a scaled-down SCT had higher odds of delay. For age and country of birth, stronger associations with patient delay, and weaker associations with response delay were found. Although SCT during the COVID-19 pandemic might have had merits in prompting people to isolate or quarantine before the availability of a vaccine, the observed interval times indicate that SCT was not fast enough to have a large effect on interrupting transmission chains. Although promising, the added value of digital SCT tools remains uncertain.