{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,9]],"date-time":"2026-10-09T21:29:48Z","timestamp":1791581388659,"version":"4.3.4"},"reference-count":60,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2024,10,21]],"date-time":"2024-10-21T00:00:00Z","timestamp":1729468800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Viruses"],"abstract":"<jats:p>After disruption in the influenza circulation due to the emergence of SARS-CoV-2, the intensity of seasonal outbreaks has returned to the pre-pandemic levels. This study aimed to evaluate the evolution and variability of whole-genome sequences of A(H1N1)pdm09, the predominant influenza virus in Sicily (Italy) during the season 2023\u20132024. The potential vaccine efficacy was calculated using the pepitope model based on amino acid changes in the dominant epitope of hemagglutinin. The HA gene sequences showed several amino acid substitutions, some of which were within the major antigenic sites. The phylogenetic analysis showed that Sicilian strains grouped into two main genetic clades (6B.1A.5a.2a.1 and 6B.1A.5a.2a) and several subclades. Notably, about 40% of sequences partially drifted from the WHO-recommended vaccine strain A\/Victoria\/4897\/2022 for the Northern Hemisphere. These sequences mostly belonged to the subclades C.1.8 and C.1.9 and harboured the amino acid mutations responsible for the modest predicted vaccine efficacy (E = 38.12% of 53%, pepitope = 0) against these viruses. Amino acid substitutions in other gene segments were also found. Since influenza viruses are constantly evolving, genomic surveillance is crucial in monitoring their molecular evolution and the occurrence of genetic and antigenic changes, and, thus, their potential impact on vaccine efficacy.<\/jats:p>","DOI":"10.3390\/v16101644","type":"journal-article","created":{"date-parts":[[2024,10,21]],"date-time":"2024-10-21T08:53:11Z","timestamp":1729500791000},"page":"1644","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Insights into Genetic and Antigenic Characteristics of Influenza A(H1N1)pdm09 Viruses Circulating in Sicily During the Surveillance Season 2023\u20132024: The Potential Effect on the Seasonal Vaccine Effectiveness"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0108-4608","authenticated-orcid":false,"given":"Fabio","family":"Tramuto","sequence":"first","affiliation":[{"name":"Department of Health Promotion Sciences Maternal and Infant Care, Internal Medicine and Medical Specialties \u201cG. D\u2019Alessandro\u201d-Hygiene Section, University of Palermo, 90127 Palermo, Italy"},{"name":"Regional Reference Laboratory for Molecular Surveillance of Influenza, Clinical Epidemiology Unit, University Hospital \u201cPaolo Giaccone\u201d, 90127 Palermo, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6989-9259","authenticated-orcid":false,"given":"Carmelo Massimo","family":"Maida","sequence":"additional","affiliation":[{"name":"Department of Health Promotion Sciences Maternal and Infant Care, Internal Medicine and Medical Specialties \u201cG. D\u2019Alessandro\u201d-Hygiene Section, University of Palermo, 90127 Palermo, Italy"},{"name":"Regional Reference Laboratory for Molecular Surveillance of Influenza, Clinical Epidemiology Unit, University Hospital \u201cPaolo Giaccone\u201d, 90127 Palermo, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1139-0879","authenticated-orcid":false,"given":"Giulia","family":"Randazzo","sequence":"additional","affiliation":[{"name":"Regional Reference Laboratory for Molecular Surveillance of Influenza, Clinical Epidemiology Unit, University Hospital \u201cPaolo Giaccone\u201d, 90127 Palermo, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Adriana","family":"Previti","sequence":"additional","affiliation":[{"name":"Regional Reference Laboratory for Molecular Surveillance of Influenza, Clinical Epidemiology Unit, University Hospital \u201cPaolo Giaccone\u201d, 90127 Palermo, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Giuseppe","family":"Sferlazza","sequence":"additional","affiliation":[{"name":"Regional Reference Laboratory for Molecular Surveillance of Influenza, Clinical Epidemiology Unit, University Hospital \u201cPaolo Giaccone\u201d, 90127 Palermo, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5851-5256","authenticated-orcid":false,"given":"Giorgio","family":"Graziano","sequence":"additional","affiliation":[{"name":"Regional Reference Laboratory for Molecular Surveillance of Influenza, Clinical Epidemiology Unit, University Hospital \u201cPaolo Giaccone\u201d, 90127 Palermo, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3397-7331","authenticated-orcid":false,"given":"Claudio","family":"Costantino","sequence":"additional","affiliation":[{"name":"Department of Health Promotion Sciences Maternal and Infant Care, Internal Medicine and Medical Specialties \u201cG. D\u2019Alessandro\u201d-Hygiene Section, University of Palermo, 90127 Palermo, Italy"},{"name":"Regional Reference Laboratory for Molecular Surveillance of Influenza, Clinical Epidemiology Unit, University Hospital \u201cPaolo Giaccone\u201d, 90127 Palermo, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5090-1366","authenticated-orcid":false,"given":"Walter","family":"Mazzucco","sequence":"additional","affiliation":[{"name":"Department of Health Promotion Sciences Maternal and Infant Care, Internal Medicine and Medical Specialties \u201cG. D\u2019Alessandro\u201d-Hygiene Section, University of Palermo, 90127 Palermo, Italy"},{"name":"Regional Reference Laboratory for Molecular Surveillance of Influenza, Clinical Epidemiology Unit, University Hospital \u201cPaolo Giaccone\u201d, 90127 Palermo, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Francesco","family":"Vitale","sequence":"additional","affiliation":[{"name":"Department of Health Promotion Sciences Maternal and Infant Care, Internal Medicine and Medical Specialties \u201cG. D\u2019Alessandro\u201d-Hygiene Section, University of Palermo, 90127 Palermo, Italy"},{"name":"Regional Reference Laboratory for Molecular Surveillance of Influenza, Clinical Epidemiology Unit, University Hospital \u201cPaolo Giaccone\u201d, 90127 Palermo, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,10,21]]},"reference":[{"key":"ref_1","unstructured":"World Health Organization (WHO) (2024, September 13). Estimating Disease Burden of Influenza, Available online: https:\/\/www.who.int\/europe\/activities\/estimating-disease-burden-of-influenza."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"862","DOI":"10.1111\/irv.12985","article-title":"Predictors of influenza severity among hospitalized adults with laboratory confirmed influenza: Analysis of nine influenza seasons from the Valencia region, Spain","volume":"16","author":"Derqui","year":"2022","journal-title":"Influenza Other Respir. 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