Epidemiology and economic burden of medically attended influenza and influenza-like illness in Germany, 2016–2019

Older adults and individuals with certain underlying conditions are at elevated risk of severe influenza complications. This study quantifies the burden of influenza and influenza-like illness (ILI) in Germany focusing on these high-risk groups. This cohort study is based on claims data of a large statutory health insurance fund. Influenza/ILI was identified through International Classification of Diseases version 10 (ICD-10) codes J09-J11. Among insured individuals, the incidence of medically attended influenza/ILI, hospitalizations, complications, and direct healthcare costs were estimated for three consecutive influenza seasons from 2016–2017 to 2018–2019. Healthcare resource use, complications, and costs attributable to influenza were estimated through comparison with a matched control group. Analyses were stratified by age and prevalence of underlying conditions. Approximately 7 million individuals were included in each season. Influenza/ILI incidence decreased with age, but hospitalizations were most common among older adults. One in five cases aged 80+ years was hospitalized. In all age groups, individuals with underlying conditions had a higher incidence of influenza/ILI and of complications than those without underlying conditions. Direct costs per influenza/ILI case ranged from €133.28 (2016–2017) to €218.99 (2018–2019) and were higher in older adults and in individuals with underlying conditions. Underdiagnosis and misclassification of influenza in administrative claims may occur, particularly in the outpatient setting. Only selected complications were examined; exclusion of cardiovascular and neurological consequences likely results in an underestimation of the influenza/ILI burden. Indirect costs, e.g. through productivity losses are not considered. Influenza/ILI significantly impacts the German healthcare system, with older adults and individuals with underlying conditions contributing disproportionately to the observed burden. Risks of severe outcomes and direct costs are highest in older adults, particularly those aged 80+ years, while children with underlying conditions also contribute substantially to the observed burden. These groups are important targets for preventive interventions. Influenza (flu) is a common respiratory infection that can cause serious illness, particularly in older adults and people with long-term health conditions. This study examined how often people in Germany were diagnosed with the flu or flu-like illness, how many were hospitalized, how often certain complications occurred, and what it cost the healthcare system. We used health insurance records from one of Germany’s largest public health insurers, covering approximately 7 million people per year across three flu seasons (2016–2019). We identified flu cases using diagnostic codes and compared them to a matched group of people without flu to estimate the true impact of the illness. Flu was most commonly diagnosed in young children, but hospitalization was far more frequent in older adults. One in five people aged 80 years and older who were diagnosed with the flu required hospital treatment. People with underlying health conditions—such as heart disease, respiratory conditions, or weakened immune systems—were more likely to be diagnosed with flu, to develop complications, and be hospitalized. The average direct healthcare cost per flu case ranged from €133 to €219 per season, rising to over €800 in adults aged 80 and above. Across Germany, total flu-related direct costs were estimated at between €105 million and €228 million per season, with roughly half attributable to people aged 60 and older. These findings highlight the importance of targeted vaccination programs for older adults and people with underlying health conditions to reduce the burden of flu in Germany.

老年人群及存在基础疾病的个体，罹患流感重症并发症的风险显著升高。本研究聚焦上述高危群体，量化了德国境内流感及流感样病例（influenza-like illness, ILI）的疾病负担。
本队列研究基于某大型法定健康保险基金的理赔数据开展，通过国际疾病分类第十版（International Classification of Diseases 10th Revision, ICD-10）编码J09-J11识别流感/ILI病例。研究针对2016-2017至2018-2019年连续三个流感季，估算了参保人群中因医就诊的流感/ILI发病率、住院率、并发症发生率及直接医疗成本。通过与匹配对照组进行对比，估算了流感相关的医疗资源消耗、并发症发生情况及相关成本。本研究按年龄及基础疾病患病率进行分层亚组分析。
每个流感季的研究纳入人群约700万。流感/ILI发病率随年龄增长呈下降趋势，但住院病例以老年人群最为集中，80岁及以上群体中每5名流感/ILI患者即有1名需住院治疗。各年龄组中，存在基础疾病的个体流感/ILI发病率及并发症发生率均显著高于无基础疾病者。每例流感/ILI患者的直接医疗成本介于133.28欧元（2016-2017季）至218.99欧元（2018-2019季）之间，老年人群及存在基础疾病的个体相关成本更高。
行政理赔数据中可能存在流感漏诊及分类错误的情况，尤以门诊场景为甚。本研究仅考察了部分并发症，未纳入心血管及神经系统相关结局，因此可能低估了流感/ILI的实际疾病负担。此外，研究未考虑生产力损失等间接医疗成本。
流感/ILI对德国医疗体系造成了显著负担，老年人群及存在基础疾病的个体对整体疾病负担的贡献远超其人口占比。重症结局风险及直接医疗成本在老年人群中最高，尤以80岁及以上群体为甚；而合并基础疾病的儿童群体同样对整体疾病负担贡献显著。上述群体是流感预防干预的重点目标人群。
流感是一类常见呼吸道传染病，可引发重症疾病，尤其对老年人群及长期存在基础疾病的个体威胁更显著。本研究针对德国人群，调查了流感/流感样病例的确诊频率、住院人数、特定并发症发生率及医疗体系相关成本。研究使用德国某大型公立健康保险机构的参保记录，覆盖2016-2019年三个流感季、每年约700万参保人群。研究人员通过诊断编码识别流感病例，并与未患流感的匹配对照组进行对比，以估算流感的真实疾病影响。流感/ILI的确诊以幼儿最为常见，但住院率在老年人群中显著更高：80岁及以上的确诊流感患者中，每5人即有1人需住院治疗。存在基础疾病（如心脏病、呼吸系统疾病或免疫功能低下）的个体，确诊流感、发生并发症及住院的风险均更高。每例流感患者的平均直接医疗成本介于133欧元至219欧元每季度，80岁及以上成人的相关成本则超过800欧元。经估算，德国境内每个流感季的流感相关直接医疗总成本介于1.05亿欧元至2.28亿欧元之间，其中约一半来自60岁及以上人群。本研究结果凸显了针对老年人群及基础疾病患者开展靶向疫苗接种项目的重要性，以降低德国境内的流感疾病负担。