To reduce influenza-associated morbidity and mortality, countries in South America recommend annual influenza vaccination for persons at high risk for severe influenza illness, including young children, persons with preexisting health conditions, and older adults. Interim estimates of influenza vaccine effectiveness (VE) from Southern Hemisphere countries can provide early information about the protective effects of vaccination and help guide Northern Hemisphere countries in advance of their season. Using data from a multicountry network, investigators estimated interim VE against influenza-associated severe acute respiratory illness (SARI) hospitalization using a test-negative case-control design. During March 13-July 19, 2024, Argentina, Brazil, Chile, Paraguay, and Uruguay identified 11,751 influenza-associated SARI cases; on average, 21.3% of patients were vaccinated against influenza, and the adjusted VE against hospitalization was 34.5%. The adjusted VE against the predominating subtype A(H3N2) was 36.5% and against A(H1N1)pdm09 was 37.1%. These interim VE estimates suggest that although the proportion of hospitalized patients who were vaccinated was modest, vaccination with the Southern Hemisphere influenza vaccine significantly lowered the risk for hospitalization. Northern Hemisphere countries should, therefore, anticipate the need for robust influenza vaccination campaigns and early antiviral treatment to achieve optimal protection against influenza-associated complications.

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2024 年南半球流感疫苗预防流感相关住院的临时有效性估计 - REVELAC-i 网络，南美洲五个国家，2024 年 3 月至 7 月。


为了降低与流感相关的发病率和死亡率，南美洲国家建议每年为严重流感疾病高危人群（包括幼儿、已有健康状况的人和老年人）接种流感疫苗。南半球国家流感疫苗有效性 (VE) 的临时估计可以提供有关疫苗接种保护作用的早期信息，并有助于在季节到来之前为北半球国家提供指导。研究人员利用来自多国网络的数据，采用测试阴性病例对照设计，估算了流感相关严重急性呼吸道疾病 (SARI) 住院治疗的临时 VE。 2024年3月13日至7月19日期间，阿根廷、巴西、智利、巴拉圭和乌拉圭共发现11,751例流感相关SARSI病例；平均而言，21.3%的患者接种了流感疫苗，调整后的住院VE率为34.5%。针对主要亚型 A(H3N2) 的调整后 VE 为 36.5%，针对 A(H1N1)pdm09 的调整后 VE 为 37.1%。这些临时 VE 估计表明，尽管接种疫苗的住院患者比例不大，但接种南半球流感疫苗可显着降低住院风险。因此，北半球国家应预见到需要开展强有力的流感疫苗接种运动和早期抗病毒治疗，以实现针对流感相关并发症的最佳保护。