Who's first to get flu? Preschoolers

But it may end up being just as important to prevent flu in the group most likely to spread it -- preschoolers, says John Brownstein, lead author of the study and a researcher in the Children's Hospital Informatics Program. "This would provide a different approach to vaccination," he says. "This would be more of a public health approach to vaccinate people on the front lines who may spread it to other people."

Three- and 4-year-olds are not at higher risk for flu complications. But, he says, vaccinating them would mean they infect fewer people.

The Advisory Committee on Immunization Practices for the federal Centers for Disease Control and Prevention is considering expanding flu vaccine recommendations to preschoolers, says Dr. William Schaffner, chairman of the department of preventive medicine at Vanderbilt University School of Medicine and a member of the advisory committee. But the agency may be reluctant to act now, only one year after a major snafu in the supply line caused a severe national vaccine shortage.

"Everyone is leery of making expanded recommendations because the vaccine supply has, from time to time, been insecure," Schaffner says. "But if the vaccine supplies remain firm, people should expect to see recommendations expanded further, with preschoolers and school-age children the next target."

Flu vaccine supplies are expected to be adequate for the 2005-2006 season, according to federal health officials.

Adding preschoolers to the flu vaccine recommendation plan would also require discussions about logistics and cost, says Dr. Margaret Rennels, a professor of pediatrics at the University of Maryland and a vaccine expert.

"In general, influenza is a very safe vaccine," Rennels says. "The main concern would be economic. You would have a lot more people coming in for the vaccine on a seasonal basis."

The discussion on vaccinating children comes at a time when experts are debating the best use for annual influenza vaccine in other age groups. A paper published last month in the Lancet showed that flu vaccine is ineffective in reducing cases of the flu in people age 65 and older although it does significantly reduce the severity of illness, resulting in fewer flurelated hospitalizations and deaths.

Most likely, Schaffner says, the CDC will continue to recommend flu vaccine for the groups who suffer the most when infected. But other groups could be added to curb transmission.