The vast majority of children who have died of flu so far this season did not get the flu shot, the CDC reported Friday.

Less than 50% of U.S. children have gotten a flu shot so far this season.John Carl D`Annibale / Albany Times Union via Getty Images

Fifty-two children have died of the flu so far this season, the Centers for Disease Control and Prevention reported Friday, seemingly putting pediatric deaths on track to outpace last season`s record-breaking high.

Ninety percent of those children had not received the annual flu shot, the CDC said.

"We`re absolutely bracing ourselves," said Michele Slafkosky, executive director of the nonprofit Families Fighting Flu. "We`re concerned that we`re not even at the peak of flu season yet."

Overall flu activity picked up again last week, according to the CDC report, following several weeks of decline. The agency estimates that there`s been at least 20 million flu cases so far this season, resulting in 270,000 hospitalizations and 11,000 deaths.

It`s not uncommon to have two waves of flu in a single season, especially as one strain replaces another.

While much of the flu that`s going around continues to be a flu A strain - specifically, H3N2 subclade K - a B strain has begun picking up steam.

Surveillance data from the past several flu seasons shows upticks in flu in January and February after late December spikes.

More sick kids, fewer vaccinations

This season has also seen the highest rate of children hospitalized with the flu in 15 years, according to Friday`s report.

By the end of December, the CDC said, the weekly rate of kids under age 18 hospitalized for flu had reached the highest level observed since the 2010-2011 season.

And for the week ending Jan. 24, the percentage of emergency department visits that resulted in a diagnosis of flu saw an increase among kids 5 to 17 years old, while either remaining stable or falling for all other age groups.

The increase in kids getting severely ill with the flu comes as vaccination rates continue to fall.

As of Jan. 17, fewer than half of children 6 months to 17 years old - 45.1% - had received the flu shot this season. During the 2019-2020 flu season, 63.7% were vaccinated.

The 2024-2025 season was the deadliest on record for kids, with 289 pediatric flu deaths. By this time last year, 47 kids had died.

Earlier this month, the Trump administration upended longstanding childhood vaccine recommendations, doing away with guidance that all children should get a yearly flu shot starting at 6 months, recommending instead that parents consult with their pediatricians about whether their kids should get a flu shot.

Major medical organizations including American Academy of Pediatrics decried the changes and continue to recommend the yearly flu shots.

"How can you not see a correlation of more deaths and more hospitalizations with less vaccinations?" Slafkosky said. "I can`t stress it enough: It`s not too late to get a flu shot. It may not keep you from getting the flu, but it may prevent you from more serious complications, and keep you and your children out of the hospital."