Flu activity is low, but experts worry about a new strain and vaccination rates

NEW YORK– The U.S. flu season is off to a slow start and it’s unclear whether it will be as severe as last winter’s, but some health experts are concerned as data from the U.S. Centers for Disease Control and Prevention released Friday shows a new version of the virus has emerged.

An initial analysis suggests that current vaccines may still be somewhat effective against the new version of the flu, which has been the main culprit in recent infections, according to CDC data.

Some scientists and medical professionals are more concerned about disappointing vaccination rates, a key reason flu hospitalizations and deaths were unusually high during last year’s flu season — one of the deadliest this century.

“I think we’re going to have a really tough season,” said Asefeh Faraz Covelli of the George Washington University School of Nursing.

Last winter, the overall rate of flu hospitalizations was the highest since the H1N1 pandemic 15 years ago. Flu has been the underlying or contributing cause of more than 18,000 deaths, and a seven-day period earlier this year saw more than 1,800 deaths – the highest one-week spike in at least a decade. Childhood deaths from the flu were also much higher than usual.

CDC data released Friday showed low flu activity so far, with only one state — Louisiana — reporting moderate activity. Most reported infections are among children, said the CDC’s Alicia Budd, who tracks flu infections for the Atlanta-based agency.

Most were also a new version of the type A H3N2 virus that historically has caused the most hospitalizations and deaths among older adults. This type is responsible for most flu infections so far this year, and more than half are a new subclade K variant that is different from the strain this year’s flu vaccines were designed for.

Preliminary analysis in the UK suggests the shots offer at least partial protection, although it will take some time for scientists to know exactly how effective they are. Experts say it’s important to get any protection that lessens the shock of a flu infection.

Flu seasons tend to get worse between December and February, and illnesses will likely accelerate as people travel and gather for Thanksgiving, Covelli said.

“I think it’s going to start getting better here,” she said. “Now is the perfect time to get vaccinated.”

This year, researchers faced an unusual struggle to understand changing respiratory infection and vaccination rates.

They typically rely on the CDC for data, but a recent government shutdown halted data collection and reporting just as respiratory infections began to rise.

Meanwhile, government efforts to promote disease-preventive shots have been more limited since U.S. Health Secretary Robert F. Kennedy Jr. was put in charge of the CDC and other federal health agencies. Kennedy, a leading anti-vaccine campaigner, sparked uncertainty about the safety of vaccines, including flu shots that contained a preservative called thimerosal.

Indeed, COVID-19 vaccination rates clearly continue to fall, with about 6% of children and 14% of adults up to date on their shots, according to other CDC data released Friday. Each figure is about 3 percentage points lower than it was at the same time last fall.

For influenza, vaccination trends are a little more vague. Some sources have suggested that flu vaccinations are declining. More than two million fewer flu shots were administered in U.S. pharmacies through the end of October compared to last year, according to data from IQVIA, a health information and research company.

But the latest CDC data indicates that for children, the vaccination rate this year is about the same as this time last fall, at 34%. And the adult vaccination rate rose a few percentage points to about 37%, according to CDC data, which relies on survey information.

It’s early in the season and too early to know whether the increase will be lasting or what’s causing it, CDC officials said.

As of early November, the U.S. flu hospitalization rate was about the same as at the same time in 2024. Hospitalization rates for COVID-19 and another respiratory virus, RSV, are lower so far this season, according to another CDC data set.

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