When the flu strikes, preschool kids may be the first age group affected, passing the flu on to other people, a new study shows.

If so, vaccinating 3- and 4-year-olds against flu might help curb flu epidemics, write researchers in the American Journal of Epidemiology.

Flu can be a serious illness. Every year, it kills 36,000 people in the U.S. and hospitalizes more than 200,000 people, according to the CDC. The youngest, oldest, and the ill are the most vulnerable.

Flu Vaccine: Little Evidence in Little Kids?

Current Flu Vaccine Recommendations

Flu vaccines are recommended for all babies and children aged 6 to 23 months. They are also recommended for adults and children 6 months and older with high-risk medical conditions such as chronic heart and lung conditions, including asthma.

The CDC also recommends yearly flu shots for these groups:

--People at high risk for complications from the flu (including elders, people in nursing homes or long-term care facilities, women who are or will become pregnant during flu season, and people with chronic health problems)

—People aged 50-64

—People who could transmit the flu to high-risk groups (including health care workers and contacts of or caregivers for babies younger than 6 months)

The CDC also recommends flu shots for hurricane evacuees aged 6 months and older who are staying in crowded group settings.

CDC Prioritizes Flu Shots Again

Flu Shots, Flu Prevention

Until Oct. 24, people in high-risk groups will get priority for the 2005 flu shot. As of Oct. 24, anyone can get a flu shot, says the CDC.

Some people may not be able to take flu shots for medical reasons. They include babies younger than 6 months, people who are allergic to chicken eggs, and those who’ve had bad reactions to flu shots in the past. Check with your doctor to see if you can get a flu shot.

The virus that causes the flu changes every year, so flu vaccines change every year. Last year’s flu vaccine won’t necessarily protect you this year against the flu.

Getting vaccinated is the single best way to prevent the flu, says the CDC. The CDC also offers these flu prevention tips:

—Avoid close contact with people who are sick.

—Stay home when you are sick.

—Cover your mouth and nose when coughing or sneezing.

—Clean your hands often.

—Avoid touching your eyes, nose, or mouth.

Flu Study

The new flu study comes from researchers including John Brownstein, PhD, of the emergency medicine division of Children’s Hospital Boston and the pediatrics department of Harvard Medical School.

Brownstein’s team checked medical records of flu patients at six Massachusetts health care settings, including hospitals and a large group medical practice, from January 2000 through September 2004.

Preschool-age children provided the first sign of pneumonia and influenza, the researchers report.

Flu season can begin as early as October and last as late as May, says the CDC.

In the study, 3- and 4-year-old children started showing up in hospitals and doctors’ offices with respiratory illnesses as early as late September. Younger kids began arriving a week later, older children in October, and adults in November, states a news release.

In addition, respiratory illness in kids younger than 5 years old was a stronger predictor of death than in any other age group.

’Hotbeds of Infection’

“The data make sense because preschools and daycares, with their close quarters, are hotbeds of infection,” says Brownstein in a news release.

The findings don’t prove that preschool-age kids are the first victims or main spreaders of the flu, note Brownstein and colleagues. But “this age group does appear to have an important role in influenza transmission,” they write.

The Advisory Committee on Immunization Practices is considering a recommendation to vaccinate all preschool-age children against the flu, and the study’s results support that recommendation, write the researchers.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Brownstein, J. American Journal of Epidemiology, Oct. 1, 2005; vol 162: pp 686-693. CDC: “Key Facts About Influenza and the Influenza Vaccine.” CDC: “Interim Immunization Recommendations for Individuals Displaced by Hurricane Katrina.” News release, Children’s Hospital Boston.