2003). A 10%–20% infection rate in patients with COPD can therefore generate an important increase in the demand for health services. In the adult population, hospitalization rates can be 2 to 30 times higher among high-risk adults (Table 1). Glezen and colleagues (1987) determined the frequency of high- risk of patients hospitalized with acute respiratory disease (ARD). The risk for ARD hospitalization was 19.7 per ten thousand for persons with high-risk conditions and only 9.3 for persons without. Chronic pulmonary disorders were the most common underlying conditions identiﬁed, and persons with pulmonary conditions had the greatest risk for acute respiratory disease hospitalization. The highest rate occurred among persons older than 65 years of age with pulmonary conditions (87.5 per ten thousand), and the rate was 27.5 for persons 45 to 64 years of age. Cardiac conditions were the second most frequent group of underlying disorders of patients hospitalized with ARD. Only for persons younger than 20 years of age was the risk of ARD hospitalization greater for persons with cardiac conditions than for those with pulmonary conditions (22.9 and 14.9 per ten thousand, respectively). Hospitalization rates can be 5 to 22 times higher in chil- dren who have medical conditions who put them at increase risk for inﬂuenza-related complications than in healthy indi- viduals (Table 1). Izurieta and colleagues (2000) studied hos- pitalization rates for acute respiratory-disease among infants and children aged less than 17 years during the period from 1992 to 1997, and observed that hospitalization rates were 5–20 times higher among high-risk individuals at Northern California Kaiser sites and 4–22 times higher at Group Health Cooperative sites (Table 1). Hospitalization rates among children aged <2 years at high risk for complications of in- ﬂuenza were 60 and 48 times higher at Northern California Kaiser and Group Health Cooperative sites, respectively, than among healthy individuals aged 5–17 years. Deaths from inﬂuenza are more common among persons of any age with chronic pulmonary disease and other chronic conditions (Simonsen et al 1997). Case fatality with inﬂuenza A epidemics in patients with COPD can be 30% or more, while in healthy persons the case-fatality rate can be 1–2 per 2000 cases. Combined pulmonary and cardiovascular disease can increase the risk of death by 800-fold (Barker and Mullooly 1982). Reports of 153 laboratory-conﬁrmed inﬂuenza-related pediatric deaths from 40 states during the 2003–2004 inﬂuenza season indicated that 40% were aged <2 years and 30% of those aged 2–17 years have an under- lying medical condition traditionally considered to place a International Journal of COPD 2007:2(1) Preventing inﬂuenza in COPD person at risk for inﬂuenza-related complications (Harper et al 2005). Inﬂuenza vaccination The primary strategy for reducing the effect of inﬂuenza in persons with COPD is vaccinating these patients and their contacts each year before seasonal increases in inﬂuenza virus circulation. Inﬂuenza vaccination should be recommended in patients with COPD for two reasons. Firstly, vaccination can reduce the risk of inﬂuenza-related complications and exacerbations. Secondly, when vaccine and epidemic strains are well-matched, a higher vaccination rate can reduce the risk for inﬂuenza outbreaks due to herd immunity. Inﬂuenza vaccination is recommended in the following population groups (ACP 1996; USPSTF 1996; WHO 2002; Fukuda et al 2004; Harper et al 2005; CDC 2006): • Persons aged more than 64 years • Persons aged <64 years with one or more of the follow- ing high-risk conditions for inﬂuenza-related complica- tions: Chronic pulmonary disease o Chronic heart disease o Diabetes o Renal dysfunction o Hemoglobinopathies o Cancer o Human immunodeﬁciency virus infection o Immunosuppressant treatment o Pregnant women beyond ﬁrst trimester during o inﬂuenza season o Persons aged 6 months to 18 years treated with aspirin for a long period o Children aged 6–23 months • Persons who can transmit inﬂuenza to high-risk pa- tients Two inﬂuenza vaccines are available: the inactivated tri- valent inﬂuenza vaccine (TIV), produced by Sanoﬁ-Pasteur, Chiron Corporation, and GlaxoSmithKline, and the live attenuated inﬂuenza vaccine (LAIV), produced by Med Immune Vaccines. Both inactivated inﬂuenza vaccine and LAIV are available to reduce the risk for inﬂuenza infection and illness. The differences between TIV and LAIV vaccines are pre- sented on Table 2. Inactivated inﬂuenza vaccine contains killed viruses, while LAIV contains live, attenuated viruses still capable of replication. LAIV is administered by intranasal spray, while inactivated inﬂuenza vaccine is administered intramuscularly by injection. Inactivated inﬂuenza vaccine is approved for use 45