Emergency department data demonstrate that preschool children are the first to come down with influenza each year and could play an important role in the infection's spread, according to John S. Brownstein, Ph.D., of Children's Hospital Boston, and his associates.
Data collected from four emergency departments and one ambulatory care setting in Massachusetts during 2000–2004 suggest that children aged 3–4 years are consistently the first to seek care for respiratory illness during each influenza season, and that the temporal pattern of illness in that group strongly predicts mortality due to influenza and pneumonia among people of all ages.
The results bolster arguments in favor of universal vaccination of all preschool-aged children in addition to the 6- to 23-month-olds for whom the vaccine is currently recommended, the investigators said (Am. J. Epidemiol. 2005;162:686–93).
Among patients presenting to the different health care settings—including one pediatric emergency department, one adult emergency department, and two that treat both adults and children—children aged 3–4 years presented earliest in the season, with a mean lead time of 34 days prior to the peak in overall mortality. Children of that age group presenting to pediatric emergency departments had the longest lead time of all, with a mean of 50 days. In contrast, adults aged 18 years and older in the ambulatory care and emergency department settings had a mean lead time of just 12 days.
Prediction of influenza and pneumonia mortality varied by age. Children younger than 3 years were the best predictors, explaining 41% of the deviance, while those aged 3–4 years explained 37%, the investigators reported.
“Although this finding does not necessarily prove that preschool-aged children are driving the yearly influenza epidemics, they intriguingly suggest that preschool-aged children are the initial group infected and may be important in the subsequent spread,” they wrote.
These and other data point to the idea that targeting yearly influenza vaccination to younger children may benefit the entire community. The idea is currently under consideration by the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices.