California health officials are warning that this year’s flu season could arrive earlier than usual and hit harder than expected, as a mutated H3N2 strain, low flu vaccination rates and global surges create what experts call a “calm before the storm.”
Doctors in Los Angeles County say they are already seeing worrying signs: the county has recorded its first flu death of the season, and international data from Australia, Japan, Taiwan and the U.K. show unusually early and severe flu waves, especially in children and older adults.
In a typical year, flu cases climb after Christmas and peak in January or February. This time, specialists expect a noticeable uptick weeks sooner.
“We’re expecting an early and likely sharp start to the flu season,” said infectious disease physician Dr. Elizabeth Hudson of Kaiser Permanente Southern California.
The concern centers on a recently emerged subvariant, H3N2 subclade K, which began spreading late in the summer—long after scientists had locked in the formula for this year’s flu shot back in February.
Because the vaccine was designed against earlier strains, there may be at least a partial vaccine mismatch.
Still, public health agencies stress: that does not mean the shot is useless.
According to data from the U.K., this season’s vaccine has still significantly reduced hospitalizations, especially in children, even with the new subclade circulating. And the Los Angeles County Department of Public Health continues to urge anyone who has not yet been vaccinated to get their shot before holiday gatherings.
Health officials say the flu shot remains one of the best tools to prevent severe illness, hospital stays and deaths.
Experts are also sounding the alarm about falling flu vaccination rates in both the U.S. and abroad, a trend that started during the COVID-19 pandemic and has not rebounded. Lower coverage means more people are susceptible, which creates more opportunity for the virus—including new subvariants—to spread quickly.
In Australia, only about a quarter of young children and just over 60% of seniors got their flu shots this year, the lowest in several seasons. That country logged more than 410,000 lab-confirmed cases in what officials there called a record-breaking flu year, with a particularly heavy toll on kids.
In the U.S., preliminary survey data show drops in vaccination for both children and adults compared with pre-pandemic levels. Doctors worry those gaps, combined with an evolving virus, could set up California for a rough winter.
Even with the genetic changes in H3N2 subclade K, this year’s shot is still expected to blunt the worst outcomes. Flu vaccines are rarely a perfect match, but typically cut the risk of serious illness by 30% to 60%, and they often work best in younger people.
Because of the possible mismatch, specialists say early testing and antiviral treatment will be especially important this season. Medications such as oseltamivir (Tamiflu) can substantially reduce the risk of complications when started within one to two days of symptom onset, and can be used preventively in some high-risk household contacts. At-home flu test kits—now widely available—may help people confirm infection sooner and seek timely care.
Doctors are most concerned about the very young and very old, as well as people with chronic conditions. Children under 5 are particularly vulnerable to respiratory illnesses; even a “routine” flu infection can escalate quickly in that age group.
Beyond vaccines and antivirals, public health experts still recommend familiar precautions: regular handwashing, staying away from sick individuals when possible, improving indoor ventilation and wearing a mask in crowded, high-risk spaces such as airports and airplanes.
The debate over vaccines has grown louder this year after controversial changes on the CDC website about autism and immunization, pushed by federal officials who question vaccine safety. Mainstream medical experts and former CDC leaders have strongly rejected those changes, pointing to decades of research that find no link between vaccines and autism and urging the public to rely on high-quality scientific evidence and guidance from reputable agencies like the U.S. Centers for Disease Control and Prevention.
California, along with other West Coast states, has also emphasized that state-level vaccine recommendations are based on longstanding data showing that shots such as the seasonal flu vaccine save lives and protect communities.
As one L.A. infectious disease specialist put it, this winter may bring “another year of more cases of flu”—but how severe it becomes will depend heavily on how many people get vaccinated, how quickly infections are detected and treated, and whether residents are willing to take layered precautions seriously again.
