U.S. flu infections surged over the holiday period, with 45 states reporting high or very high activity during the week of Christmas — up from 30 states the prior week — and federal health officials warning that the season is severe and likely to worsen. New government data released Monday showed that by some measures the current season already rivals last winter’s flu epidemic, one of the harshest in recent memory. The Centers for Disease Control and Prevention estimated at least 11 million illnesses, 120,000 hospitalizations, and 5,000 deaths from influenza have occurred so far this season.
The surge is being driven in large part by an influenza A H3N2 subtype known as subclade K, which differs from the strain targeted by this year’s flu vaccines — raising concern about vaccine effectiveness just as the Trump administration announced it will no longer recommend flu shots for all children.
A vaccine mismatch at a dangerous moment
Influenza A H3N2 historically causes the most hospitalizations and deaths in older people, and it is the type most frequently reported so far this season. More than 90 percent of H3N2 infections analyzed have been the subclade K variant, a version that was not included in this year’s flu vaccine formulation.
Public health experts said the mismatch is especially concerning given where the season stands.
“The fact that we’ve seen steady increases over the last several weeks without much of a decline or even a flattening would suggest to me that we’ve got the peak ahead of us,” said Dr. Robert Hopkins, medical director of the National Foundation for Infectious Diseases.
Flu seasons typically do not peak until January or February.
Children and young adults showing severe rates
Nine pediatric flu deaths have been reported so far this season. Among children, the percentage of emergency department visits due to flu has already surpassed the highest level recorded during the 2024-2025 season.
Hopkins said H3N2 typically hits older adults hardest, and the elevated rates among children and young adults point to a season likely to be severe across all age groups. The percentage of doctor’s office and clinic visits attributed to flu-like illness was also higher in late December than at any point during the prior season. Deaths and hospitalizations have not yet reached last year’s levels, but Hopkins noted those are lagging indicators.
Last flu season was itself exceptionally severe. The overall hospitalization rate was the highest recorded since the H1N1 flu pandemic 15 years earlier, and child flu deaths reached 288, the worst figure on record for a regular U.S. flu season.
Administration withdraws flu shot recommendation for children
New federal surveillance data on the surge was released the same day the Trump administration announced it will no longer recommend flu vaccinations for U.S. children. The administration said vaccination decisions should be made by parents and patients in consultation with their doctors.
A U.S. Department of Health and Human Services spokesperson said flu vaccines will continue to be fully covered by private insurers and federal programs, including Medicaid, the Children’s Health Insurance Program, and the Vaccines for Children program.
Health Secretary Robert F. Kennedy Jr., who was a prominent voice in the anti-vaccine movement before President Donald Trump appointed him to lead federal health agencies, framed the change as ending government pressure on physicians. “Government bureaucracies should never coerce doctors or families into accepting vaccines or penalize physicians for respecting patient choice,” Kennedy wrote on social media last week. “That practice ends now.”
Public health experts recommend that everyone 6 months of age and older receive an annual flu vaccine.
Medicaid immunization reporting to end
Hopkins also voiced concern about a separate federal notice posted last week announcing that government Medicaid programs will no longer be required to report on immunization rates. Federal health officials described the move as part of an effort to decouple how Medicaid physicians are rated and paid from how frequently they administer childhood vaccinations.
Hopkins said the change will “eliminate a major source of data” that allows communities to assess their efforts to protect children from vaccine-preventable diseases. Medicaid data covers flu vaccination as well as measles and other preventable illnesses, and provides a more comprehensive picture of immunization rates among children at elevated risk for many diseases than broader CDC survey data, he said.
“This is a disastrous plan,” Hopkins said.
COVID-19 infections have also been rising, according to other federal data, though they remain less prevalent than flu so far this winter.