Soares Patrícia, Gómez Verónica, Gaio Vânia, Santos João Almeida, Rodrigues Ana Paula, Machado Ausenda
National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal.
PLoS One. 2025 May 9;20(5):e0314177. doi: 10.1371/journal.pone.0314177. eCollection 2025.
Since the 2022-2023 season in Portugal, a high-dose quadrivalent influenza vaccine is freely available for individuals living in long-term care facilities (LTCF). In 2024-2025, vaccination was extended to community-dwelling individuals aged ≥85 years. Given the scarcity of reported high-dose influenza vaccine effectiveness (IVE) estimates for this population, this study aims to estimate the high-dose relative and absolute IVE. A retrospective cohort study using data from electronic health records databases (EHR) will be implemented, using two cohorts, one of individuals vaccinated with influenza vaccine (to estimate relative IVE) and another of individuals eligible for the high-dose quadrivalent influenza vaccine (to estimate absolute IVE). We will consider two subgroups for both cohorts: individuals living in LTCF and community-dwelling individuals aged ≥85. We will use a fixed cohort approach, defining the eligible population by age at the vaccination campaign(s) start and living status. The outcomes are based on the primary cause of hospital admission. The reference population database will be defined by linking EHR on vaccination, comorbidities, and hospitalisations using a unique identifier through a deterministic data linkage procedure, and influenza vaccination status will be assessed retrospectively. We will use Cox proportional hazards regression models to estimate the hazard ratio (HR), considering as event the first hospitalisation due to influenza-like-illness and as exposure the vaccination status. IVE will be estimated as one minus the confounder-adjusted HR of vaccinated with the high-dose quadrivalent influenza vaccine vs vaccinated with standard dose (to estimate relative IVE) or unvaccinated (to estimate absolute IVE). While challenges such as EHR constraints and potential reporting bias pose limitations, using routinely collected data has successfully estimated COVID-19 VE and enables precise monitoring of VE with higher representativeness. The results of this study will inform the Health Ministry on the future influenza vaccine programme in Portugal.
自2022 - 2023赛季起，在葡萄牙，长期护理机构（LTCF）中的居民可免费接种高剂量四价流感疫苗。2024 - 2025年，疫苗接种范围扩大至85岁及以上的社区居民。鉴于针对该人群的高剂量流感疫苗有效性（IVE）估计数据稀缺，本研究旨在估计高剂量流感疫苗的相对和绝对IVE。将开展一项回顾性队列研究，利用电子健康记录数据库（EHR）的数据，设立两个队列，一个是接种流感疫苗的个体队列（用于估计相对IVE），另一个是符合接种高剂量四价流感疫苗条件的个体队列（用于估计绝对IVE）。我们将为两个队列各考虑两个亚组：长期护理机构中的居民以及85岁及以上的社区居民。我们将采用固定队列方法，根据疫苗接种活动开始时的年龄和居住状况来界定符合条件的人群。结局基于入院的主要原因。参考人群数据库将通过确定性数据链接程序，使用唯一标识符将疫苗接种、合并症和住院情况的电子健康记录相链接来定义，并且将对流感疫苗接种状况进行回顾性评估。我们将使用Cox比例风险回归模型来估计风险比（HR），将因流感样疾病首次住院视为事件，将疫苗接种状况视为暴露因素。IVE将被估计为1减去高剂量四价流感疫苗接种者与标准剂量接种者（用于估计相对IVE）或未接种者（用于估计绝对IVE）经混杂因素调整后的HR。尽管电子健康记录限制和潜在报告偏倚等挑战存在局限性，但使用常规收集的数据已成功估计了新冠疫苗有效性（VE），并能够以更高的代表性对VE进行精确监测。本研究结果将为葡萄牙卫生部制定未来的流感疫苗计划提供参考。
