A new study has shown that flu killed more U.S. children than chicken pox, whooping cough, and measles combined in the 2003-2004 flu season.
Researchers say this suggests that children should be vaccinated as aggressively as the elderly.
According to the study of 153 children killed by flu in that particular winter, nearly two-thirds were under age 5.
The study leaders Niranjan Bhat and Jennifer Wright of the Centers for Disease Control and Prevention, found the highest death rate was among infants under 6 months.
It seems that while people with underlying medical problems typically face the greatest risk of death from the flu, nearly half the youngsters who died in the 2003-2004 season seemed to have no underlying medical problems, such as asthma or heart disease.
Bhat says it was surprising that almost one half were previously healthy.
The survey which is the first to systematically use laboratory tests to confirm fatal flu cases, also showed that influenza can become really severe very quickly, and almost one-third died outside a hospital setting, and one-third died after only 3 days of illness.
In general the vast majority of children struck by the flu recover without problems.
Bhat says that preliminary numbers from last year's flu season show that the number of childhood deaths was much lower, just over 40.
But it was not until last year that the federal Advisory Committee on Immunization Practices recommended a flu shot for all children age 6 to 23 months.
The research team says that it is likely that, during the 2003-2004 season, more deaths among children were associated with influenza than with any other currently vaccine-preventable disease in the United States.
They also say that increased influenza-vaccine coverage and early identification and effective treatment of influenza among children should be key goals.
The childhood death rate is dwarfed by the overall death rate from the flu, which typically kills 36,000 Americans and a half million people globally.
It seems that only about 65 percent of seniors get the recommended flu shot.
The childhood flu death rate in 2003-2004 may actually have been higher because testing for influenza was not done in all cases where children died of lung illness and, in some areas, tests were not done at the beginning of the season.
But another factor may be that the strain of flu common that year, known as H3N2, carries a higher rate of death in general.
Until October 2004 doctors were not required to report a childhood death caused by influenza.
Raphael Dolin of Harvard Medical School commenting on the study, says it may be important to vaccinate children against the flu because they often help spread it.
However, vaccines do not work in infants under 6 months, so in those cases, vaccinating mothers and pregnant women might provide the best protection.
A year ago, many people had trouble getting flu shots because one manufacturer lost its license and half the doses destined for the United States had to be destroyed.
The study appears in The New England Journal of Medicine.