gms | German Medical Science

Background: Systematic live monitoring of acute public health threats, such as the SARS-CoV-2 pandemic, is necessary to derive evidence-based and targeted measures. The aim of this study was to develop, establish, and evaluate a surveillance and early warning system for SARS-CoV-2 infections that can be rapidly deployed in public health emergencies.

Methods: SentiSurv RLP is an app-based surveillance and early warning system based on five sentinel cohorts in the largest and geographically well-distributed cities in Rhineland-Palatinate (Mainz, Koblenz, Trier, Kaiserslautern, and Ludwigshafen). Participants were aged 18 years or older and were randomly selected by registration offices to reflect the age and sex distribution of each city. Based on a sample size calculation, a minimum number of 14,000 individuals was targeted, including 2,800 individuals in each city. In phase 1 (December 2022 to April 2023), participants were required to conduct SARS-CoV-2 rapid antigen self-tests twice a week. In phase 2 (June 2023 to December 2023) and phase 3 (January 2024 to March 2024), testing frequency was reduced to once a week. A smartphone-based application was used to transmit test results and symptoms of the SARS-CoV-2 infection in case of a positive test, and to characterize the participants through a questionnaire-based interview. This included sociodemographic information, health risk factors, comorbidities, and medication. Participants were also asked to complete weekly changing questionnaires, which were tailored to the evolving pandemic situation. Incidence estimates were made publicly available on a dashboard.

Results: In total, 19,925 individuals participated in SentiSurv RLP. Mean age was 50.1 (±15.7) years with a range from 18-93 years. The proportion of women was 54.1% and 17.7% had a migration background. The majority of participants had high educational attainment (57.3%) and were employed (65.8%). Median equivalized income was 2.620€ (interquartile range 1.850€/3.750€). Differences in response were observed between cities, with Mainz having the highest response (7.4%) and Ludwigshafen the lowest (2.7%). In terms of the initial characterization, 99% of the participants were partially characterized and 84% were fully characterized. Of 703,860 data files transmitted, 580,605 were SARS-CoV-2 test results. Throughout all phases, 70% of the participants adhered to regularly conducting the self-tests. Two peaks of SARS-CoV-2 incidence were detected on 23 February 2023 (7-day incidence 3,074, 95% confidence interval [CI] 2,597; 3,611) and 13 December 2023 (7-day incidence 3,928 [95% CI 3,570; 4,312]), with Mainz having the highest incidence at both time points. The public's perception of lifting the face mask requirement on public transport in March 2023 was mixed, with 41.4% [95% CI 40.2%; 42.6%] rating the lifting as inappropriate and 45.5% [95% CI 44.3%; 46.7%] rating it as appropriate.

Conclusion: The SentiSurv RLP app-based surveillance system has proven to be a viable and valid tool for collecting real-time data to accurately monitor the SARS-CoV-2 pandemic. The app serves as a communication platform to obtain health data and situation assessments from the population in real time and to rapidly disseminate information to the public.

There are no conflicts of interest reported regarding this work. Outside the submitted work, PSW reports grants from Bayer AG, non-financial grants from Philips Medical Systems, grants and consulting fees from Boehringer Ingelheim, grants and consulting fees from Novartis Pharma, grants and consulting fees from Sanofi-Aventis, grants, consulting and lecturing fees from Bayer Health Care, grants and consulting fees from Daiichi Sankyo Europe, lecturing fees from Pfizer Pharma, lecturing fees from Bristol Myers Squibb, consulting fees from Astra Zeneca, consulting fees and non-financial support from Diasorin and non-financial support from IEM. PSW is funded by the Federal Ministry of Education and Research (BMBF 01EO1503), Ministry of Science and Health of the State of Rhineland Palatinate (MWG RLP 724-0010#2021/0030-1501), and the Federal Institute for Occupational Safety and Health (BAuA, F2447 / 537727) outside the present work. PSW is principal investigator of the German Center for Cardiovascular Research (DZHK) and principal investigator of the DIASyM research core (BMBF DIASyM research core (BMBF 161L0217A, 031L0217A).

The authors declare that a positive ethics committee vote has been obtained.