Flu Symptoms in Kids Can Turn Deadly Fast. Know These Signs, Doctors Say

The United States is facing one of its most severe flu seasons in decades, data show. Infections and hospitalizations are surging, driven by a new mutated influenza A variant, H3N2 “subclade K.”

Experts warn that flu activity could keep raging for weeks and urge people to get vaccinated. But unlike past years, parents may have to jump through extra hoops to get their children a flu shot.

On Jan. 5, the Centers for Disease Control and Prevention dropped its long-held universal flu vaccine recommendation for kids 6 months and older, instead saying the shot should only be given after a discussion with a health care provider.

The shift comes as the flu is hitting children hard. At least 32 children have died from flu so far this season, per the CDC. The weekly pediatric flu hospitalization rate has peaked at the highest level seen since 2010, NBC News reported.

Flu metrics have already surpassed last flu season, one of the deadliest for children in 20-plus years.

The 2024-2025 flu season led to 280 flu-related pediatric deaths, the highest number since the CDC started reporting these in 2004 (excluding the 2009-2010 swine flu pandemic), the agency said. Nearly all of those children were unvaccinated.

“It’s more than unfortunate; it’s tragic,” Dr. Yvonne Maldonado, a pediatric infectious disease epidemiologist and professor at Stanford University, tells TODAY.com of the CDC’s change to its flu shot guidance for kids.

“(Flu shots) probably are the most effective intervention in the last 100 years to reduce child deaths in this country,” she says.

The change drew also criticism from leading medical groups, including the American Academy of Pediatrics and the Infectious Disease Society of America.

While top health officials justified the change by claiming there was insufficient scientific evidence behind the universal recommendation, many medical experts disagree.

“There is plenty of data showing the effectiveness … of the influenza vaccine in children,” Dr. Pedro Piedra, professor of molecular virology and pediatrics at Baylor College of Medicine, tells TODAY.com — including several studies still listed on the CDC website.

The CDC website also still states that “the flu vaccine can prevent severe, life-threatening complications in children.”

The experts warn that the new guidance creates confusion, which could lead to fewer children getting vaccinated.

As it’s impossible to predict which child may become severely ill from the flu, here’s what parents should know about the flu shot in kids and how fast symptoms can turn deadly.

Flu Vaccine Effectiveness in Children

The flu shot works by introducing bits of killed or weakened flu virus to the immune system, which trains the body to make antibodies that can recognize and fight off the virus.

While the flu shot doesn’t always prevent infection, the goal is to reduce the severity of symptoms. “If you are vaccinated, you’re less likely to end up in the hospital, on a ventilator, or dying from flu,” says Maldonado.

Flu shot effectiveness ranges from 40-60% depending on the season, but research suggests it’s even higher among kids.

A 2022 study listed on the CDC site that showed flu vaccination reduced the risk of severe illness in children by 75%.

A 2020 study also on the CDC site showed the flu shot reduced flu-related hospitalization by 41% and ER visits by 50% among children during the severe 2017-2018 flu season.

In 2017, a first-of-its-kind study demonstrated that flu vaccination reduces a child’s risk of dying from the flu by up to 65% for healthy children.

“If you look back every year at who’s been hospitalized and who’s died from flu, the overwhelming majority are unvaccinated,” says Maldonado.

Last season, 89% of the children who died from flu were not vaccinated, per CDC data.

So far this season, data from the U.K. Health Security Agency suggest that the 2025-2026 flu vaccine is 70-75% effective at reducing hospitalizations among children.

So, even it isn’t a perfect match to the flu strains circulating this year, the shot still offers protection, experts note.

The Flu Can Be Deadly for Any Child

About half of the 280 children who died flu last season had an underlying medical condition; the rest were previously healthy.

“Children have the highest infection rates of all groups because they have not seen the virus as often as adults,” says Piedra.

In any given flu season, there are multiple strains circulating, and “many kids have not had an infection with those different strains,” Piedra explains. “If they get infected, other than vaccination they don’t have any inherent protection.”

Children under 2 and those with underlying conditions are at the highest risk. However, most children who become hospitalized from flu are healthy, says Maldonado.

Every year, an average of 100-200 children die from the flu in the U.S. These deaths occur from severe complications such as pneumonia, encephalitis or myocarditis, says Piedra.

“Over 50% of the children that die don’t have any (underlying condition) … but if you look at vaccination status, the vast majority have not been vaccinated,” Piedra adds.

Flu Complications Can Cause Permanent Damage

Even if children recover, flu complications can cause lasting damage.

If the flu affects the brain or central nervous system, it can lead to seizures, learning disorders or difficulty with motor function, says Piedra.

Recently, there has been a rise in a rare, severe neurological complication among children called influenza-associated encephalopathy. “Overnight, these kids just went into comas. It was really frightening,” Maldonado explains.

The most severe form, necrotizing encephalopathy — where “the brain is rotting,” says Piedra — can cause permanent brain damage and disability.

“I’ve seen a kid who was mute from bad (brain swelling). … The flu can do so many things, it’s unbelievable,” Dr. Jason Newland, chief of infectious disease at Nationwide Children’s Hospital, tells TODAY.com.

Vaccination is the best way to protect against severe flu and its complications, the experts note.

Severe Flu Symptoms in Children

The flu can progress rapidly in children. Although most will recover on their own, it’s important for parents to monitor for severe symptoms.

“If you look at (pediatric) deaths, about 25% of children die before they see a physician, and 25% die in the emergency room,” says Piedra.

Often, flu begins with a sudden fever. “Your child is healthy in the morning. Then by the afternoon, they have a fever that’s 103, 104,” says Piedra.

Common symptoms include fatigue, muscle aches, headache, sore throat and coughing. Flu can also cause shortness of breath, says Piedra.

Kids often develop gastrointestinal symptoms like vomiting and diarrhea, says Maldonado. They can become dehydrated, which causes dark urine, dry lips or dizziness.

“They may be more quiet or not recognize things well,” Piedra. Little kids can become fussy and irritable.

The flu can also trigger a type of muscle inflammation called myositis, especially in the calf muscles, Dr. Daniel Park, medical director of UNC Children’s emergency department, tells TODAY.com. “If a child is having trouble walking or tiptoe walking, that’s an indication get checked out.”

Flu antivirals, such as oseltamivir, can help reduce symptoms — but these are most effective when taken early, says Maldonado.

If a child has severe or lingering symptoms, a high fever (over 104), trouble breathing, dehydration, extreme lethargy or chest pain, seek medical attention, the experts urge.

“Parents know their child. When something is out of the norm, take your child to see a physician,” says Piedra.

It’s Not Too Late to the Get Flu Shot

The flu vaccine is still available for all children 6 months and older after a conversation with a health care provider. It comes in a shot or nasal spray, which can be given by a parent at home, says Piedra. He adds that he’s continuing to advise all kids get vaccinated against the flu.

Talk to your doctor or pharmacist if you have questions. Despite the CDC guidance changes, it is sill covered by insurance.

“Getting a yearly flu vaccination is the best way to reduce the risk from flu and its potentially serious complications,” the CDC says on its web page for the 2025-2026 season.

Flu shot protects against multiple strains, including flu B, which often surges later in the season.

As flu season continues, Maldonado has one piece of advice for concerned parents: “Trust your pediatrician.”

“Children should not be dying from a disease that’s preventable,” she adds.