Influenza infections in the U.S. spiked over the holiday period, with health authorities characterizing this as a severe flu season that is likely to worsen further.
New government data released on Monday—tracking flu activity through the week of Christmas—revealed that by some metrics, this season has already outpaced last winter’s flu epidemic, one of the most severe in recent history.
This data was made public on the same day the Trump administration announced it will cover flu shots and certain other types of vaccines for all children.
During the Christmas week, 45 states reported high or very high flu activity, up from 30 states previously.
Public health experts note that the elevated numbers seem to be driven by the specific strain of flu circulating.
One flu virus subtype, H3N2, has historically caused the highest rates of hospitalizations and deaths among older adults. So far this season, this has been the most frequently reported strain. More concerningly, over 90% of analyzed H3N2 infections are a new variant—known as the subclade K variant—that differs from the strain included in this year’s flu vaccines.
Flu seasons typically do not reach their peak until January or February, so it remains too early to gauge the full impact of this mismatch.
“The fact that we’ve observed steady increases over the past several weeks without significant decline or even stabilization suggests to me that the peak lies ahead,” said Dr. Robert Hopkins, medical director of the National Foundation for Infectious Diseases.
The second consecutive severe flu season
Last flu season was severe, with the overall flu hospitalization rate reaching its highest level since the H1N1 flu pandemic 15 years ago. [Metric] reached 288, the worst recorded for a regular U.S. flu season.
Nine pediatric flu deaths have been reported so far this season. For children, the percentage of emergency department visits due to flu has already exceeded the highest mark seen during the 2024-2025 season.
Hopkins noted that H3N2 typically affects older adults most severely, and rising rates among children and young adults indicate a severe flu season across all age groups.
Another worrying sign: The percentage of doctor’s office and medical clinic visits for flu-like illness was also higher late last month than at any point during the previous flu season.
Deaths and hospitalizations have not yet reached last year’s levels, though Hopkins emphasized these are lagging indicators.
The U.S. Centers for Disease Control and Prevention estimates that at least 11 million illnesses, 120,000 hospitalizations, and 5,000 deaths from flu have already occurred this season.
U.S. government scales back vaccine recommendations
Public health experts advise that everyone 6 months and older should receive an annual influenza vaccine.
However, federal health officials announced on Monday they will no longer formally recommend flu vaccinations for U.S. children, stating the decision should be made by parents and patients in consultation with their physicians.
Nonetheless, a U.S. Department of Health and Human Services spokesperson confirmed that 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.
Data show COVID-19 infections have also been rising, though they remain less prevalent than flu this winter. The Trump administration [action] COVID-19 shots for healthy children last year.
U.S. to halt Medicaid data collection
Hopkins expressed concern over a [document] posted last week stating that government Medicaid programs, which fund medical services for low-income families, will no longer be required to report on immunization rates.
CDC [data] suggests U.S. flu vaccination rates are roughly on par with last year. However, he noted that Medicaid data—covering flu, measles, and other pathogens—offers a more comprehensive view of children at higher risk for various diseases.
Federal health officials framed the move as part of an effort to separate how Medicaid doctors are evaluated and compensated from their rates of administering childhood vaccinations.
“Government bureaucracies should never pressure doctors or families into accepting vaccines or penalize physicians for respecting patient choice,” wrote Health Secretary [Name], a prominent voice in the anti-vaccine community before President Donald Trump appointed them to lead federal health agencies.
“That practice ends now,” Kennedy wrote in [document] last week.
But Hopkins argued the move will “remove a major data source” that enables communities to assess efforts to protect children from vaccine-preventable diseases.
“This is a disastrous plan,” he added.
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