BACKGROUND
Worldwide, efforts are being made to stop the COVID-19 pandemic caused by SARS-CoV-2. Contact tracing and quarantining are key in limiting SARS-CoV-2 transmission. Mathematical models have shown that the time between symptom onset and isolation of cases and isolation of contacts are the most important components that determine whether the pandemic can be controlled. Mobile contact tracing applications could accelerate the tracing and quarantining of contacts by automatically detecting and notifying contacts.
OBJECTIVE
This study aimed to assess the use of a national Dutch contact tracing app and its determinants among individuals diagnosed with SARS-CoV-2 infection.
METHODS
We used anonymized SARS-CoV-2 routine contact tracing data collected between October 28th 2020 and February 26th 2021 in the region of Amsterdam, the Netherlands. Complete case logistic regression analysis was performed to identify determinants of using the app. Continuous variables were modelled as B-splines due to their non-linear relationship.
RESULTS
Of 29,766 SARS-CoV-2 positive cases, 4,824 (16.2%) reported app use. Median age of the population was 41 (IQR 29-55) years and 46.7% were male. In multivariable analysis, males (aOR 1.11, 95%CI 1.04-1.18) and residents of municipalities surrounding Amsterdam were more likely to use the app (Aalsmeer aOR 1.34, 95%CI 1.13-1.58;Ouder-Amstel aOR 1.96, 95%CI 1.54-2.50), while those born outside the Netherlands, particularly those born in non-western countries (aOR 0.33, 95%CI 0.30-0.36), were less likely to use the app. Odds of app use increased with age until age 58 and decreased sharply thereafter (P<.001). Odds of app use increased with number of contacts, peaked at 8 contacts, and then decreased (P<.001). Individuals working in day-care, home-care and elderly nursing homes were less likely to use the app.
CONCLUSIONS
Contact tracing app use is low in the region of Amsterdam. To increase the impact of the app on SARS-CoV-2 control, attempts should be made to increase app use in general and especially among younger people, those born outside the Netherlands, and people with many contacts. Furthermore the app could be made more attractive by adding extra features like test result, local risk or vaccination status.