Any parent knows that when a preschooler gets the flu, it won't be long before the rest of the family is bedridden too. Three- and 4-year-olds are infamous for their runny noses and spewing coughs, not to mention their indifference to tissues and hand-washing.
Now, however, experts think this beloved age group is doing more than infecting their families. A new study suggests that 3- and 4-year-olds may be powerful drivers of annual influenza outbreaks.
The findings could lead to changes in the nation's strategy on flu vaccination.
The study, from Children's Hospital Boston, showed that preschool-age children are the first to show up each year in emergency rooms and clinics with flu, a pattern that typically begins in late September. Babies younger than 2 tend to arrive with symptoms a week or two later, while older children begin to arrive in October. Adults don't generally show up until November.
Moreover, preschoolers may foreshadow the severity of any given influenza season. As the number of babies and preschoolers with the flu increased in the study, so too did flu-related deaths in the elderly.
Preschoolers are thought to be robust flu-spreaders because of their poor hygiene, close contact with other children and because they shed the virus -- remain infectious -- longer than other age groups.
"It's well known that preschoolers introduce flu into households. But what was not previously described is that children are leading off the epidemic," says Dr. Kenneth Mandl, an attending emergency room physician at Children's Hospital Boston and coauthor of the study. "Not only do preschoolers come in first, they can be used as sentinels, giving a three-week window into the future. That's a very important surveillance and early warning function."
The study, published in the Oct. 1 issue of the American Journal of Epidemiology, used a computerized biosurveillance system to collect data from five healthcare settings in the Boston area from 2000 through 2004.
The findings are expected to rekindle interest among public health officials in expanding flu vaccine recommendations to 3- and 4-year-olds. Under the current plan, the government recommends flu vaccine for people at high risk for developing complications or dying, such as the elderly, infants and chronically ill individuals.
Last year, the CDC began recommending vaccines for babies ages 6 to 23 months because studies show children younger than 2 have hospitalization rates second only to people age 65 and older.
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.
"It could turn out that preventing the young kids from spreading it to the elderly could, in fact, reduce flu in this group that isn't getting the protection we once thought," Mandl says.
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First on the list
The federal government currently recommends that these groups, who are at higher risk for complications, receive the annual influenza vaccine:
* People age 65 and older
* Residents of long-term-care facilities
* People age 2 or older with chronic disease conditions
* Children ages 6 to 23 months
* Pregnant women
* Healthcare workers who provide direct patient care
* Household contacts and out-of-home caregivers of children younger than 6 months.For flu shots, contact your healthcare provider or county health department.
* The L.A. County Department of Health Services will list dates and locations for its flu shot clinics at www.ladhs.org beginning tomorrow.
* Similar information is available from the Orange County Health Care Agency at www.ochealthinfo.com, from the Riverside County Department of Public Health at www.rivcoph.org and from the Ventura County Health Care Agency at www.vchca.org (click on "Public Health Bulletins"). Residents of San Bernardino County can call (909) 387-6521.