Document is current

Article History

Received: 23 October 2025

Accepted: 23 April 2026

First Online: 11 May 2026

Declarations

:

: This study is part of a coordinated network project comprising a retrospective observational study and a prospective study. It adhered to applicable legislation, the Guidelines for Ethics Committees in Italy by the Italian National Bioethics Committee (2014), and the Declaration of Helsinki. The protocol for the prospective component received approval from the relevant Ethics Committee (Comitato Etico Val Padana, ASST Cremona, Cremona, Italy; Study Code 83-2023-OSS_ALTRO-CR61). The retrospective component was conducted in accordance with the EU General Data Protection Regulation (Reg. EU 2016/679, Articles 6(1)(e) and 9(2)(j)), the Italian Legislative Decree No. 196 of 30 June 2003, as amended by Legislative Decree No. 101 of 10 August 2018 (Personal Data Protection Code), and the Ethical Rules for Processing Personal Data for Statistical and Scientific Research Purposes adopted by the Italian Data Protection Authority on 5 June 2019. The legal basis for data processing was Article 6(1)(e) GDPR (public interest) and Article 9(2)(j) GDPR (scientific research). Consent to participate was not applicable, because analyses were based on data routinely collected by the Agency for Health Protection ( Agenzia di Tutela della Salute , ATS) of Milan, a public body of the Regional Health Service of the Lombardy Region. Under Lombardy Regional Laws nos. 23/2015 and 22/2021, the institutional functions of the ATS include the evaluation of the health status of the population, the governance of individual care pathways within the regional social and health-care system, and the evaluation of services provided and patient outcomes among residents in the covered area. The study of the characteristics, determinants, and health outcomes of long Covid by the ATS is specifically grounded in the Deliberation of the Regional Government of Lombardy no. 3720/2024. The data were accessed for research purposes on 18–23 October 2024. All datasets were anonymized and linked via a unique identifier before analysis.

: Not applicable.

: Owing to the nature of this study and data privacy constraints, patients and members of the public were not involved in the design, analysis, or interpretation of the study.

: The authors declare no competing interests.

: Claudio Lucifora 3 , Daria Vigani 3,4 , Federico Franzoni 3 , Gabriele Letta 3 , Laura Antolini 2 , Giuseppe Lapadula 2 , Elena Tassistro 2 , Maria Grazia Valsecchi 2 , Stefano Denicolai 4 , Marica Grego 4 , Diala Kabbara 4 , Costanza Baldrighi 4 , Antonio Giampiero Russo 1 , Pietro Magnoni 1 , Cristina Mazzali 1 , Alberto Milanese 1 , Rossella Murtas 1 , Andrea Salvatori 1 , Deborah Testa 1 , Sara Tunesi 1 , Adele Zanfino 1 , Simona Dalle Carbonare 5 , Federica Manzoni 5 , Simona Migliazza 5 , Pietro Giovanni Perotti 5 , Linda Guarda 6 , Marco Villa 6 , Silvia Tillati 7 , Giacomo Crotti 7 , Giuseppe Sampietro 7 , Alberto Zucchi 7 , Anita Andreano 8 , Luca Cavalieri d’Oro 8 , Elisabetta Merlo 8 , Magda Rognoni 8 , Piersimone Fontana 9 , Giovanni Maifredi 9 , Ivan Cometti 10 , Anna Clara Fanetti 10 , Maria Letizia Gambino 11 , Monica Lanzoni 11 , Giuseppe Emanuele La Piana 12 , Anna Bussi 13 , Vincenzo Belcastro 14 , Stefano Rusconi 15 , Luigi Magnani 16 , Maurizio Morlotti 17 , Andrea Patroni 17 , Raffaele Bruno 18 , Elisabetta Pagani 18 , Paolo Sacchi 18 and Valentina Zuccaro 18 . 1 Epidemiology Unit, Agency for Health Protection Milan, Milan, Italy. 2 University of Milano-Bicocca, School of Medicine and Surgery and Bicocca Bioinformatics Biostatistics and Bioimaging Centre (B4), Milan, Italy. 3 Department of Economics and Finance, Catholic University of the Sacred Heart, Milan, Italy. 4 Department of Economics and Management, University of Pavia, Pavia, Italy. 5 Epidemiology Unit, Agency for Health Protection Pavia, Pavia, Italy. 6 Epidemiology Unit, Agency for Health Protection Val Padana, Cremona, Italy. 7 Epidemiology Unit, Agency for Health Protection Bergamo, Bergamo, Italy. 8 Epidemiology Unit, Agency for Health Protection Brianza, Monza, Italy. 9 Epidemiology Unit, Agency for Health Protection Brescia, Brescia, Italy. 10 Epidemiology Unit, Agency for Health Protection Montagna, Sondrio, Italy. 11 Epidemiology Unit, Agency for Health Protection Insubria, Varese, Italy. 12 Respiratory Rehabilitation Unit, ASST Crema – Ospedale Santa Marta Rivolta D’Adda, Crema, Italy. 13 General Medicine Unit, ASST del Garda – Presidio Ospedaliero di Manerbio/Leno. 14 Neurology Unit, ASST Lodi – Ospedale Maggiore di Lodi, Lodi, Italy. 15 Infectious Diseases Unit, ASST Ovest Milanese – Ospedale di Legnano, Legnano, Italy. 16 Internal Medicine Unit, ASST Pavia – Ospedale Civile di Voghera, Voghera, Italy. 17 ASST Valcamonica, Brescia, Italy. 18 Fondazione IRCCS Policlinico San Matteo, Pavia, Italy.