Burden of influenza in the elderly: a narrative review

This review provides an update on specificities of influenza in older adults (≥65-year-old), including epidemiology, burden in terms of hospitalization and mortality, extra-respiratory complications and specific challenges of prevention.

In the past 2 years, influenza activity was drastically reduced by barrier measures implemented during the COVID-19 pandemic. A recent French epidemiological study covering 2010-2018 epidemic seasons estimated that 75% of costs induced by influenza-associated hospitalizations and complications were attributable to older adults, a population bearing more than 90% of influenza-associated excess mortality.In addition to their age, comorbidities and reduced vaccine response, long-term facility residents are at risk for nosocomial outbreaks. Beyond respiratory complications, influenza triggers acute myocardial infarction and ischemic stroke. Influenza might drive significant functional loss in frail older adults, which can lead to "catastrophic" or severe disability in up to 10% of patients. Vaccination remains the cornerstone of prevention, with enhanced immunization strategies (i.e., high-dose or adjuvanted formulations) to be largely implemented in older adults. Efforts to increase influenza vaccination uptake during the COVID-19 pandemic should be consolidated.

Burden of influenza in the elderly is largely under-recognized, especially the cardiovascular complications and the impact on functional status, justifying more effective preventive strategies.