AUTHOR=Speierer Alexandre , Chocano-Bedoya Patricia O. , Anker Daniela , Schmid Alexia , Keidel Dirk , Vermes Thomas , Imboden Medea , Levati Sara , Franscella Giovanni , Corna Laurie , Amati Rebecca , Harju Erika , Luedi Chantal , Michel Gisela , Veys-Takeuchi Caroline , Zuppinger Claire , Nusslé Semira Gonseth , D’Acremont Valérie , Tall Ismaël , Salberg Éric , Baysson Hélène , Lorthe Elsa , Pennacchio Francesco , Frei Anja , Kaufmann Marco , Geigges Marco , West Erin Ashley , Schwab Nathalie , Cullati Stéphane , Chiolero Arnaud , Kahlert Christian , Stringhini Silvia , Vollrath Fabian , Probst-Hensch Nicole , Rodondi Nicolas , Puhan Milo A. , von Wyl Viktor 

TITLE=The Corona Immunitas Digital Follow-Up eCohort to Monitor Impacts of the SARS-CoV-2 Pandemic in Switzerland: Study Protocol and First Results

JOURNAL=International Journal of Public Health

VOLUME=67

YEAR=2022

URL=https://www.ssph-journal.org/journals/international-journal-of-public-health/articles/10.3389/ijph.2022.1604506

DOI=10.3389/ijph.2022.1604506

ISSN=1661-8564

ABSTRACT=<p><bold>Objectives:</bold> To describe the rationale, organization, and procedures of the Corona Immunitas Digital Follow-Up (CI-DFU) eCohort and to characterize participants at baseline.</p><p><bold>Methods:</bold> Participants of Corona Immunitas, a population-based nationwide SARS-CoV-2 seroprevalence study in Switzerland, were invited to join the CI-DFU eCohort in 11 study centres. Weekly online questonnaires cover health status changes, prevention measures adherence, and social impacts. Monthly questionnaires cover additional prevention adherence, contact tracing apps use, vaccination and vaccine hesitancy, and socio-economic changes.</p><p><bold>Results:</bold> We report data from the 5 centres that enrolled in the CI-DFU between June and October 2020 (covering Basel City/Land, Fribourg, Neuchâtel, Ticino, Zurich). As of February 2021, 4636 participants were enrolled and 85,693 weekly and 27,817 monthly questionnaires were collected. Design-based oversampling led to overrepresentation of individuals aged 65+ years. People with higher education and income were more likely to enroll and be retained.</p><p><bold>Conclusion:</bold> Broad enrolment and robust retention of participants enables scientifically sound monitoring of pandemic impacts, prevention, and vaccination progress. The CI-DFU eCohort demonstrates proof-of-principle for large-scale, federated eCohort study designs based on jointly agreed principles and transparent governance.</p>