Seasonal influenza epidemics occur each year as a result of minor changes in the antigenic characteristics of the hemagglutinin and neuraminidase glycoproteins of the influenza viruses (antigenic drift) [2] . The morbidity and mortality associated with seasonal influenza outbreaks are significant, especially in older patients, who incur more than 90% of the influenza-related mortality each year [3] . Factors contributing to their increased vulnerability include a decline in cellmediated and humoral immune responses, a reduction in lung compliance and respiratory muscle strength, a diminished cough reflex associated with normal aging, the frequent presence of multiple comorbid conditions, nutritional deficiencies, and in the case of residents of long-term care facilities, greater exposure risk due to close living quarters and shared caregivers [4, 5] .