Flu season has already killed 20 children in U.S.

In Michigan, 15-year-old Joshua Polehna died two weeks ago after suffering flu-like symptoms. The Lake Fenton High School student was the state's fourth pediatric flu death this year, according to published reports.

And in Texas, the town of Flower Mound mourned Schwolert, a healthy, lanky 17-year-old who loved to golf and taught Sunday school at the church where his father was a youth pastor.

Late last month, he and his family drove 16 hours to spend the holidays with his grandparents in Amery, Wis., a small town near the Minnesota state line. Max felt fluish on Christmas Eve, seemed better the next morning but grew worse that night. The family decided to postpone the drive home and took him to a local hospital. He was transferred to a medical center in St. Paul, Minn., where he died on Dec. 29.

He'd been accepted to Oklahoma State University before the Christmas trip. And an acceptance letter from the University of Minnesota arrived in Texas while Max was sick in Minnesota, his uncle said.

Nearly 1,400 people attended a memorial service for Max two weeks ago in Texas.

"He exuded care and love for other people," Phil Schwolert said.

"The bottom line is take care of your kids, be close to your kids," he said.

On average, an estimated 24,000 Americans die each flu season, according to the Centers for Disease Control and Prevention.

People who are elderly and with chronic health conditions are generally at greatest risk from flu and its complications.

The current vaccine is about 60 percent effective, and is considered the best protection available. Max Schwolert had not been vaccinated, nor had the majority of the other pediatric deaths.

Even if kids are vaccinated, parents should be watchful for unusually severe symptoms, said Lyn Finelli of the CDC.