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.