Volume 5, Number 5—October 1999
The Economic Impact of Pandemic Influenza in the United States: Priorities for Intervention
|Age group (yrs)||Percentage of all casesa|
|Percentage at high riskc|
aThe actual number of cases will depend upon the assumed gross attack rate. The distribution of cases was based on lower and upper estimates of age-specific attack rates from the 1918, 1928-29, and 1957 epidemics and pandemics (19).
bTotals do not add to exactly 100% because of rounding.
cPersons are categorized at high risk if they have a preexisting medical condition that makes them more susceptible to influenza-related complications. The percentages of age groups at high risk were obtained from the Working Group on Influenza Pandemic Preparedness and Emergency Response (GrIPPE, unpub. data). The Advisory Committee on Immunization Practices estimates that 27 to 31 million persons aged <65 years are at high risk for influenza-associated complications (17).
dAverage is an age-weighted average, using each age group's proportion of the total U.S. population.