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Epidemiologic and economic burden of 2010-11 seasonal influenza in the Unites States
Although universal annual influenza vaccination has been recommended by the Advisory Committee on Immunization Practices (ACIP) and it has lessened cases of seasonal influenza in the United States, annual seasonal influenza outbreaks continue. The ACIP initially recommended influenza vaccination for high-risk groups defined by age, occupation and medical conditions. Influenza is a public health problem and can cause severe illnesses and deaths especially in high- risk populations.
OBJECTIVE
The purpose of this study is to estimate the economic burden of 2010-11 seasonal influenza in the United States.
METHOD
Using population-based surveillance data and the results of previous studies, we estimated the number of influenza cases and influenza-attributable outpatient visits, inpatient hospitalizations, and deaths by age and risk condition during the 2010-11 influenza season. Using data from health insurance claims, this study determines the indirect, out-of-pocket, and medical costs of medically-attended influenza illness. Costs are measured in 2010 US dollars.
RESULTS
We estimated that there were approximately 22 (15-34) million cases of influenza, 11,335,518 (95% CI 6,182,189 - 15,008,412) outpatient visits, 169,856 (95% CI 113,586 - 260,268) hospitalization, and 36,957 (95% CI 27,181-50,584) deaths in the US. The prevalence of high-risk conditions for influenza in the US population varied depending on age groups: 7 for 6 month-4 year, 12% for 5-19, 20% for 20-64, and 47. for 65+. The proportions of elderly cases that obtained outpatient medical care were 88 percent for the high risk group and 60 percent for the non-high risk group. For all age groups, the rate of influenza-related hospitalizations for the high risk group was nearly twice that of the non-high risk group. Annual direct medical cost and projected lost earnings due to influenza and loss of life are estimated.
POLICY IMPLICATION
Despite limitations in our model for estimating influenza burden, namely difficulties incorporating the effects of herd immunity, and antigenic mismatch between vaccine and wild viruses, we estimate a significant economic impact of influenza in the United States. Precise estimates of Influenza-attributable morbidity and mortality can lead to better projections of the economic impact of influenza vaccination program in the total population and the high risk population. Our results suggest an economic argument for continued attention and efforts towards prevention and control of seasonal influenza.