NEW YORK — More U.S. children have died this flu season than at any time since the swine flu pandemic 15 years ago, according to a federal report released Friday.

The 216 pediatric deaths reported by the Centers for Disease Control and Prevention eclipse the 207 reported last year. It’s the most since the 2009-2010 H1N1 global flu pandemic.

It’s a startlingly high number, given that the flu season is still going on. The final pediatric death tally for the 2023-2024 flu season wasn’t counted until autumn.

“This number that we have now is almost certainly an undercount, and one that – when the season is declared over, and they compile all the data – it’s almost certain to go up,” said Dr. Sean O’Leary, of the American Academy of Pediatrics.

There are likely several contributors to this season’s severity, but a big one is that fewer children are getting flu shots, added O’Leary, a University of Colorado pediatric infectious diseases specialist.

The flu vaccination rate for U.S. children has plummeted from about 64% five years ago to 49% this season.

Flu vaccinations may not prevent people from coming down with symptoms, but research shows they are highly effective at preventing hospitalizations and deaths, O’Leary said.

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The season has not only been hard on children. CDC officials have described it as ” highly severe,” and estimate that so far there have been at least 47 million illnesses, 610,000 hospitalizations and 26,000 deaths this season.

CDC officials have information about underlying conditions on nearly 5,200 adults who were hospitalized with flu this season, and 95% had at least one existing health problem. But among 2,000 hospitalized children with more detailed health information, only about 53% had an underlying condition – including asthma and obesity.

The CDC report did not say how many of the children who died were vaccinated. The agency did not make an expert available to talk about the flu season.

The good news is that flu indicators have been waning since February, and last week all 50 states were reporting low or minimal flu activity.

The season has seen more of a mix of flu strain circulating than in many other years, with two different Type A strains – H1N1 and H3N2 – causing a lot of infections. But CDC data released earlier this year suggested flu shots were doing a pretty good job at preventing deaths and hospitalizations.

The CDC continues to recommend that everyone ages 6 months and older get an annual flu vaccine.

Childhood vaccinations in general have been declining, driven by online misinformation and the political schism that emerged around COVID-19 vaccines. Robert F. Kennedy Jr. has also echoed some of the rhetoric of antivaccine activists since taking over as the nation’s health secretary.

But there may be other reasons fewer children got flu shots this year, O’Leary said.

Many pediatricians offices are understaffed and are not holding as many after-hours vaccination clinics as in the past. Also, more Americans are getting their vaccinations at pharmacies, but some drugstores don’t vaccinate children, he said.

“My hope is that this season will be a bit of wake up call for folks that we actually do need to vaccinate our kids against influenza,” O’Leary said.

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