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Informed consent was obtained from each participant at the enrolment in the study. The study was approved by the Ethical review committees from each hospital: Eticko Povjerenstvo Hrvatskog zavoda za javno zdravstvo (HZJZ) Croatia, Zagreb: 381-15-21-3; Tartu \u00dclikooli inimuuringute eetika komitee, Estonia: 382\/M-7; Clinical research ethics committee, Galway University Hospital, Ireland: C.A. 2693; SJH\/TUH Joint Research Ethics Committee, Ireland: 0513; Fondazione Policlinico Universitario A. Gemelli IRCCS, Universit\u00e0 Cattolica del Sacro Cuore, Dipartimento di Sicurezza e Bioetica, Rome, Italy : 00372\/23; Universit\u00e0 degli Studi di Milano-Bicocca presented same approval as Policlinico Gemelli, Universit\u00e0 Cattolica del Sacro Cuore, Rome, Italy from the National Institute of Infectious Diseases, Spalanzzani IRCCS; Ethics Committee for Clinical Research at Pauls Stradins Clinical University Hospital, Latvia: 241023 - 3L; Ethics Committee for Clinical Research at Pauls Stradins Clinical University Hospital, extended to Children Clinical University Hospital, Latvia: 241023 - 10L; Ethic Committee Name: Komisja Etyki I Nadzoru nad Badaniami na Ludziach I Zwierzetach przy Centralnyum Szpitalu Klinicznym MSWIA w Warszawie, Poland, Warszawie: 15\/2022; Comiss\u00e3o de \u00c9tica para a Sa\u00fade, INSA Doutor Ricardo Jorge, Portugal: INSA-IM60_05; Comisia de Etica a Spitalului Clinic de Boli Infectioase si Tropicale \u201cDr. Victor Babes\u201d, Romania: 14420; Comisia Locala de Etica a Spitalului Universitar de Urgenta Militar Central \u201cCarol Davila\u201d, Romania: 646; Ethic Committee Name: Comisia de Etica a Cercetarii-Dezvoltarii din cadrul Institutului National pentru Sanatatea Mamei si Copilului \u201cAlessandrescu-Rusescu\u201d, Approval Code: 1464, Approval Date: 18 January 2023; Comit\u00e9 de \u00c9tica de la Investigaci\u00f3n de la Comunidad Aut\u00f3noma de Arag\u00f3n (CEICA), HU Miguel Servet, Zaragoza, Spain: PI21-176 and PI22\/483; Comit\u00e9 De \u00c9tica De La Investigaci\u00f3n Con Medicamentos, Sant Joan de D\u00e9u, Fundacio de Recerca, Barcelona, Spain: 17\/2023.","order":2,"name":"Ethics","group":{"name":"EthicsHeading","label":"Ethics approval and consent to participate"}},{"value":"Not applicable.","order":3,"name":"Ethics","group":{"name":"EthicsHeading","label":"Consent for publication"}},{"value":"M.L.M, A.M, and L.C reported receiving additional funds from the European Union Research and Innovation programme Horizon Europe (ISIDORe \u2013 Grant Agreement Number 101046133) for conducting local SARS-CoV-2 sequencing. CPP and S.A.F reported speaker fees from and participation in the advisory boards of Pfizer and M.S.D. S.A.F reports also participating in the Advisory Board of Gilead. C.M.A reported speaker fees from M.S.D, Pfizer and Sanofi. J.S reported support for attending the ESID conference 2022 from Takeda Pharmaceutical. R.H and S.P reported a grant attributed to their institution on \u201cPSCD Longitudinal evaluation of SARS-CoV-2 immune status post-natural infection and post-vaccination\u201d. C.M.A reported speaker fees from M.S.D. All other authors declare no conflicts of interest related to this work.","order":4,"name":"Ethics","group":{"name":"EthicsHeading","label":"Competing interests"}}],"article-number":"697"}}