Each year from October to May, millions across the United States come down with the flu.
According to the Centers for Disease Control and Prevention, kids get the flu more often than others. So Duval County is taking preventative measures.
Doctors say everyone older than 6 months should get a flu vaccine.
"Immunizations are the safest and most effective medical intervention we have, and we need to get many of our kids immunized as possible," said Dr. Mobeen Rathore, of UF Health Jacksonville.
But the vaccine comes at a cost some parents can't afford, and many times the flu takes infected children out of school for days.
"We need to do a better job of making sure our kids are exposed to high level instruction in the classroom, but we also know there are other obstacles to students learning, and oftentimes that is health," Duval County Superintendent Nikolai Vitti said.
That's why the Duval County Health Department and Duval County Public Schools administered the flu vaccine Monday with a parent's consent to pre-K through fifth graders at 22 schools, all at no cost.
Health insurance companies and other local foundations picked up the bill.
Former Jaguar Tony Boselli said his foundation wanted to help in this initiative because it not only helps the kids but the parents, too.
"A lot of time it starts with the young people who bring it home, parents get sick and miss work, and spreads to the elderly," Boselli said.
Flu vaccines aren't just available as a shot but also as a nasal mist called FluMist, making it easier on young children who may fear needles. That's how the children received the vaccine Monday.
Third-grader Bethany Tyler said the flu mist was quick and easy.
"Because you don't get a shot. Shots hurt worse," she said.
The nasal mist contains weakened live flu viruses. As a result, it is only for healthy people between 2 and 49 years old.