THURSDAY, July 6, 2006 (HealthDay News) -- Many more young children than previously thought are stricken with the flu each year, a new U.S. study finds. And researchers say doctors often fail to diagnose the illness, increasing the likelihood that children are spreading the disease.
"The burden of influenza was very high" among young children, said Dr. Katherine Poehling, lead author of the report and assistant professor of pediatrics at Vanderbilt Children's Hospital in Nashville, Tenn.
The findings are a good argument for making sure children in this age group get vaccinated against seasonal flu. "Vaccination has been shown to decrease infection rates and severity of the illness as well as the ability of patients to transmit the virus," said Dr. Michael Marcus, director of pediatric pulmonology/allergy at Maimonides Medical Center in New York City. "For all three reasons, vaccination is a good thing."
Results of the study were first reported to the federal Advisory Committee on Immunization Practices (ACIP) in February, and formed the basis for new recommendations that children six months to five years of age be inoculated for the flu every year. The prior ACIP recommendation, made in 2004, was that all children aged six to 23 months receive the annual influenza vaccine.
Yet, drawing on data from 2000 to 2004, the study authors found that doctors often failed to recognize flu in young children. A correct diagnosis was only given 28 percent of the time to pediatric patients hospitalized with the disease, and just 17 percent of the time to outpatients, the researchers said.
More than one-third -- 35 percent -- of the children studied visited a doctor or clinic within two days of the onset of the flu, meaning antiviral medication may have been useful.
Dr. Jonathan McCullers, assistant member in the department of infectious diseases at St. Jude Children's Research Hospital in Memphis, Tenn., said the study findings are "really, really good support for what the ACIP is doing. Eventually we think they are going to push for all kids [to be vaccinated] and I really applaud this because the burden of the disease is huge."
Until 2002, annual flu shots were recommended only for children older than six months when they had certain co-existing conditions.
"We would like for doctors to do the tests and give the children antivirals so we don't have those hospitalizations and bad outcomes," McCullers said.
Marcus added: "These children not only get sick from influenza but spread it to other children and to adults, to parents, grandparents, babysitters. They are an important vector for influenza to spread to the rest of population."
According to the study authors, rates of hospitalization and outpatient visits for influenza in young children had not been well documented.
For the study, the researchers looked at children younger than 5 years of age in three U.S. counties who had visited a doctor for an acute respiratory tract infection or fever. Nasal and throat swabs were tested for the flu virus and parents were asked whether their child had been vaccinated. Children who were hospitalized between 2000 and 2004 were also followed.
The study, appearing in the July 6 issue of the New England Journal of Medicine, is one of the first to look at this data prospectively, rather than relying on backdated records. This makes the findings particularly robust, McCullers said.
The authors calculated that the average annual rates of hospitalization for influenza were 4.5 per 1,000 children aged 0 to 5 months of age; 0.9 per 1,000 children 6 months to 23 months of age; and 0.3 per 1,000 children 24 to 59 months of age.
The authors also discovered that 50 clinic visits and six emergency-department visits per 1,000 children were attributable to the flu during the 2002-03 flu season, as were 95 clinic visits and 27 emergency-room visits per 1,000 children during the 2003-04 season.
The authors concluded that pediatric outpatient visits due to the flu were 10 to 250 times more frequent than hospitalizations, and "few influenza infections were recognized clinically."
For more information on the flu and the flu vaccine, visit the U.S. Centers for Disease Control and Prevention.