Trajectories of Seroprevalence and Neutralizing Activity of Antibodies against SARS-CoV-2 in Southern Switzerland between July 2020 and July 2021: An Ongoing, Prospective Population-Based Cohort Study

Rebecca Amati, Giovanni Piumatti, Giovanni Franscella, Peter Buttaroni, Anne-Linda Camerini, Laurie Corna, Sara Levati, Marta Fadda, Maddalena Fiordelli, Anna Maria Annoni, Kleona Bezani, Antonio Amendola, Cristina Fragoso Corti, Serena Sabatini, Marco Kaufmann, Anja Frei, Milo Alan Puhan, Luca Crivelli, Emiliano Albanese () and on behalf of the Corona Immunitas Ticino Study Group
Additional contact information
Rebecca Amati: Institute of Public Health, Faculty of Biomedical Sciences, Università della Svizzera italiana, 6900 Lugano, Switzerland
Giovanni Piumatti: Fondazione Agnelli, 10125 Turin, Italy
Giovanni Franscella: Institute of Public Health, Faculty of Biomedical Sciences, Università della Svizzera italiana, 6900 Lugano, Switzerland
Peter Buttaroni: Faculty of Informatics, Università della Svizzera italiana, 6900 Lugano, Switzerland
Anne-Linda Camerini: Institute of Public Health, Faculty of Biomedical Sciences, Università della Svizzera italiana, 6900 Lugano, Switzerland
Laurie Corna: Department of Business Economics, Health and Social Care, University of Applied Sciences and Arts of Southern Switzerland, 6928 Manno, Switzerland
Sara Levati: Department of Business Economics, Health and Social Care, University of Applied Sciences and Arts of Southern Switzerland, 6928 Manno, Switzerland
Marta Fadda: Institute of Public Health, Faculty of Biomedical Sciences, Università della Svizzera italiana, 6900 Lugano, Switzerland
Maddalena Fiordelli: Institute of Public Health, Faculty of Biomedical Sciences, Università della Svizzera italiana, 6900 Lugano, Switzerland
Anna Maria Annoni: Institute of Public Health, Faculty of Biomedical Sciences, Università della Svizzera italiana, 6900 Lugano, Switzerland
Kleona Bezani: Institute of Public Health, Faculty of Biomedical Sciences, Università della Svizzera italiana, 6900 Lugano, Switzerland
Antonio Amendola: Department of Business Economics, Health and Social Care, University of Applied Sciences and Arts of Southern Switzerland, 6928 Manno, Switzerland
Cristina Fragoso Corti: Institute of Microbiology, University of Applied Sciences and Arts of Southern Switzerland, 6501 Bellinzona, Switzerland
Serena Sabatini: Institute of Public Health, Faculty of Biomedical Sciences, Università della Svizzera italiana, 6900 Lugano, Switzerland
Marco Kaufmann: Epidemiology, Biostatistics and Prevention Institute, University of Zurich, 8001 Zurich, Switzerland
Anja Frei: Epidemiology, Biostatistics and Prevention Institute, University of Zurich, 8001 Zurich, Switzerland
Milo Alan Puhan: Epidemiology, Biostatistics and Prevention Institute, University of Zurich, 8001 Zurich, Switzerland
Luca Crivelli: Institute of Public Health, Faculty of Biomedical Sciences, Università della Svizzera italiana, 6900 Lugano, Switzerland
Emiliano Albanese: Institute of Public Health, Faculty of Biomedical Sciences, Università della Svizzera italiana, 6900 Lugano, Switzerland
on behalf of the Corona Immunitas Ticino Study Group: Membership of the Group/Team Name is provided in the Acknowledgments.

IJERPH, 2023, vol. 20, issue 4, 1-16

Abstract: Objectives: The COVID-19 pandemic continues, and evidence on infection- and vaccine-induced immunity is key. We assessed COVID-19 immunity and the neutralizing antibody response to virus variants across age groups in the Swiss population. Study Design: We conducted a cohort study in representative community-dwelling residents aged five years or older in southern Switzerland (total population 353,343), and we collected blood samples in July 2020 (in adults only, N = 646), November–December 2020 (N = 1457), and June–July 2021 (N = 885). Methods: We used a previously validated Luminex assay to measure antibodies targeting the spike (S) and the nucleocapsid (N) proteins of the virus and a high-throughput cell-free neutralization assay optimized for multiple spike protein variants. We calculated seroprevalence with a Bayesian logistic regression model accounting for the population’s sociodemographic structure and the test performance, and we compared the neutralizing activity between vaccinated and convalescent participants across virus variants. Results: The overall seroprevalence was 7.8% (95% CI: 5.4–10.4) by July 2020 and 20.2% (16.4–24.4) by December 2020. By July 2021, the overall seroprevalence increased substantially to 72.5% (69.1–76.4), with the highest estimates of 95.6% (92.8–97.8) among older adults, who developed up to 10.3 more antibodies via vaccination than after infection compared to 3.7 times more in adults. The neutralizing activity was significantly higher for vaccine-induced than infection-induced antibodies for all virus variants (all p values < 0.037). Conclusions: Vaccination chiefly contributed to the reduction in immunonaive individuals, particularly those in older age groups. Our findings on the greater neutralizing activity of vaccine-induced antibodies than infection-induced antibodies are greatly informative for future vaccination campaigns.

Keywords: COVID-19; antibodies; vaccination; cohort study; seroprevalence; acquired immunity (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2023
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