Angela Stall says her 14-month-old, Nathan, never slows down - even when he's sick.
But a couple weeks ago, she says Nathan got so sick, he could barely move.
"He was very lethargic," Angela said.
It started when Angela took him to the doctor to get a flu shot.
Within a couple hours, she says Nathan was suddenly very sick.
"He was vomiting and not himself," she said.
He didn't get better and at one point, even had a seizure.
"His eyes rolled back in his head, and he was convulsing and making a strange noise," Angela said.
Angela took him to the emergency room.
Doctors ran tests trying to figure out what was wrong with Nathan. They all came back negative.
Angela believes the flu shot made Nathan sick.
"Knowing how great he was before and how he was immediately afterwards, I think the shot did trigger some kind of illness," Angela said.
Shannon Robbins with the Visiting Nurses Association said it is possible for someone to have a severe reaction to the flu shot, but she says it's rare.
Out of 22,000 flu shots given this season by VNA, she says she's only received 17 complaints.
"Most of those are soreness at the site... arm is red or arm hurts," Robbins said.
Robbins says the benefit of getting the shot outweighs the risk.
"We know the flu kills children every year," Robbins said.
The state health department did tell FOX23 that young children who get the flu shot for the first time - like Nathan - are more likely to have a fever or feel bad for a couple days.
Angela says she probably won't give Nathan a flu shot again.
"Given everything that he went through and we went through, I don't know that I'll get one again," she said.
FOX23 called the Tulsa County health department to see if anyone else has reported problems. Someone called this week and complained of vomiting after getting a flu shot. The health department says it's investigating.
The Centers of Disease Control reports 690 complaints of adverse reactions to the flu shot.
Among those, there were three reports of young children having convulsions.
And there were two deaths.Only four percent of those were considered serious.
The CDC recommends the flu vaccine for most people over six months of age but says people allergic to eggs should not get a flu shot.