Which Kids Die of Flu?

Sept. 15, 2011 -- Being younger than 5 years old is a risk factor for severe flu, a CDC analysis of last season's child flu deaths suggests.

There were 115 confirmed child flu deaths from Sept. 1, 2010, through Aug. 31, 2011. The number includes all infants, children, and teens under age 18.

But not included is the much larger number of kids who died of flu but were not tested or officially reported, says Lyn Finelli, DrPH, chief of the CDC's surveillance and outbreak response team.

"Many, many pediatric deaths are not reported because not all kids with symptoms of flu are tested," Finelli tells WebMD. "We know this number of reported case is a fraction of pediatric flu deaths. As we do more surveillance, we will get a better picture of the true number. It is an important question."

Children only rarely die of flu. But the illness can be much more severe than most parents think. Just under half of the reported child flu deaths -- 49% -- were in kids with no underlying illness or other risk factor for severe flu.

However, 46% of kids who died last flu season were under age 5. And 29% were under age 2.

"The report underscores the fact that young age is itself a risk factor," a CDC news release notes.

Vaccine Failure

More than four out of five kids who died of flu were not fully vaccinated. That is sad, but not surprising. What seems odd is that 23% of the deaths were among kids who were fully vaccinated.

Part of the reason is that most of these fully vaccinated kids had underlying illnesses. The flu vaccine does make most of these children far less susceptible to serious flu. But underlying illness chips away at a person's immune system, making vaccines somewhat less effective than in healthy people.

And 12% of the child deaths were in fully vaccinated kids with no underlying illness. How could this happen?

"There are always vaccine failures," Finelli says. "Say a vaccine is 90% effective. You are going to see those 10% of vaccine failures in statistics on deaths and hospitalizations. It makes you think the vaccine works less well than it does. You never see the vast majority of people for whom the vaccine works."

Kids at Highest Flu Risk

The most common risk factors among kids who died of flu were neurologic conditions. Over a quarter of pediatric deaths -- 27% -- were in such kids. Conditions included:

• Moderate or severe developmental delay -- 19% of child flu deaths
• Seizure disorder -- 12% of child flu deaths
• Cerebral palsy -- 8% of child flu deaths
• Neuromuscular disorder -- 4% of child flu deaths
• Other neurological disorders -- 7% of child flu deaths

"These are the kids who die of flu every year," Finelli says. "It is very important that parents and doctors get these kids vaccinated."

Kids with underlying lung diseases, including asthma, made up 15% of child flu deaths.