Panatto Donatella, Domnich Alexander, Chironna Maria, Loconsole Daniela, Napoli Christian, Torsello Alessandra, Manini Ilaria, Montomoli Emanuele, Pariani Elena, Castaldi Silvana, Orsi Andrea, Icardi Giancarlo
Department of Health Sciences (DISSAL), University of Genoa, 16132 Genoa, Italy.
Interuniversity Research Center on Influenza and Other Transmissible Infections (CIRI-IT), 16132 Genoa, Italy.
Vaccines (Basel). 2022 Dec 30;11(1):83. doi: 10.3390/vaccines11010083.
Following an extremely low incidence of influenza during the first waves of the ongoing COVID-19 pandemic, the 2021/22 Northern Hemisphere winter season saw a resurgence of influenza virus circulation. The aim of this study was to describe epidemiology of severe acute respiratory infections (SARIs) among Italian adults and estimate the 2021/22 season influenza vaccine effectiveness. For this purpose, a test-negative case-control study was conducted in a geographically representative sample of Italian hospitals. Of 753 SARI patients analyzed, 2.5% ( = 19) tested positive for influenza, most of which belonged to the A(H3N2) subtype. Phylogenetic analysis showed that these belonged to the subclade 3C.2a1b.2a.2, which was antigenically different from the 2021/22 A(H3N2) vaccine component. Most (89.5%) cases were registered among non-vaccinated individuals, suggesting a protective effect of influenza vaccination. Due to a limited number of cases, vaccine effectiveness estimated through the Firth's penalized logistic regression was highly imprecise, being 83.4% (95% CI: 25.8-97.4%) and 83.1% (95% CI: 22.2-97.3%) against any influenza type A and A(H3N2), respectively. Exclusion of SARS-CoV-2-positive controls from the model did not significantly change the base-case estimates. Within the study limitations, influenza vaccination appeared to be effective against laboratory-confirmed SARI.
在当前新冠疫情的第一波期间流感发病率极低之后，2021/22年北半球冬季流感病毒传播有所反弹。本研究的目的是描述意大利成年人中严重急性呼吸道感染（SARI）的流行病学情况，并评估2021/22季节流感疫苗的有效性。为此，在意大利医院具有地理代表性的样本中开展了一项检测阴性病例对照研究。在分析的753例SARI患者中，2.5%（n = 19）流感检测呈阳性，其中大部分属于A(H3N2)亚型。系统发育分析表明，这些病毒属于3C.2a1b.2a.2亚分支，其抗原性与2021/22年A(H3N2)疫苗成分不同。大多数（89.5%）病例登记在未接种疫苗的个体中，提示流感疫苗具有保护作用。由于病例数量有限，通过Firth惩罚逻辑回归估计的疫苗有效性极不精确，针对任何甲型流感和A(H3N2)的疫苗有效性分别为83.4%（95%CI：25.8 - 97.4%）和83.1%（95%CI：22.2 - 97.3%）。从模型中排除新冠病毒阳性对照并未显著改变基础病例估计值。在研究局限性范围内，流感疫苗接种似乎对实验室确诊的SARI有效。
