Frailty has important implications for influenza vaccine effectiveness and outcomes of acute illness. In this session, we will focus on four main issues of frailty in relation to ‘flu:

1. Paradoxically, although frail older adults are at increased risk for influenza and its complications, vaccine effectiveness is lower among the frail. Indeed, frailty is an important confounder of vaccine effectiveness; not considering frailty in studies of influenza vaccine effectiveness will tend to underestimate vaccine effectiveness due to this “frailty bias”.
2. The public health burden of influenza is most commonly considered over acute time horizons, with a focus on morbidity (e.g., sick time and lost productivity, hospital admission, complications such as pneumonia and ventilation), and mortality. When it comes to older adults, it is important to broaden our focus to include longer term impact of influenza illness and its complications. Persistent functional decline is an important health outcome of influenza, particularly among the frail.
3. Diagnosis of influenza can be challenging in frail older adults, given that they may not present with classic symptoms of “influenza like illness”. This has implications for clinical care as well as for surveillance.
4. New influenza vaccine options are available for older adults, including adjuvanted and high dose formulations. These will be discussed.

It is important to consider the impact of frailty on influenza outcomes and vaccine effectiveness. If frailty is not taken into account, we risk underestimating both the true burden of influenza illness in this vulnerable population and the true benefits of influenza vaccination for older adults. Despite the inverse relationship between frailty and vaccine effectiveness, influenza vaccination is an important intervention to support healthy aging for older adults across the spectrum of frailty.