California could see an early start to the annual flu season as a combination of low vaccination rates and late virus mutations could make the state especially vulnerable to transmission, health experts say.
There are already warning signs. Los Angeles County recently reported its first flu death of the season, and other countries are reporting record or powerful flu seasons that started earlier than expected.
The flu usually starts just after Christmas and before New Year's, but Dr. Elizabeth Hudson, chief medical officer for Kaiser Permanente's Southern California regional infectious disease division, said she expects viral activity to increase, perhaps over the next two to three weeks.
“We expect an early and likely sharp start to the flu season,” Hudson said.
Last year's flu season was the worst in years in California, and it is not uncommon for severe flu seasons to occur back-to-back. But what's particularly worrisome this year is a combination of declining flu vaccination rates and an “empowered mutant,” according to Dr. Peter Chin-Hong, an infectious disease expert at the University of California, San Francisco.
“This could lead to more people getting infected. And as more people get infected, some of them will end up in the hospital,” Chin-Hong said.
The timing of the emergence of this new influenza subvariant, called H3N2 subclade K, is particularly problematic. It emerged near the end of the summer, long after health officials had already determined how to develop a flu vaccine this fall, a decision that was expected to be made in February.
Subclade K of H3N2 appears to be becoming dominant in Japan and the UK, Hudson said.
“It looks like there's some mismatch between the seasonal flu vaccine strains” and the new subvariant, Hudson said.
It remains unclear whether subclade K will reduce the effectiveness of this year's flu shot.
In California and the rest of the U.S., “everything is quiet, but I think it's just the calm before the storm,” Chin-Hong said. “From what we are seeing in the UK and Japan, many more people are getting flu earlier.”
Chin-Hong noted that subclade K is not very different from the strains against which flu vaccines were developed this year. And he noted data recently published in Britain that showed this season's vaccines were still effective against hospitalization.
According to the British government, vaccinated children are 70–75% less likely to require hospital care, and adults are 30–40% less likely to require hospital care. The flu vaccine is usually between 30% and 60% effective and tends to be more effective in younger people, the British government says. said.
According to the Los Angeles County Department of Public Health, even if there is some degree of mismatch between the vaccine and the circulating strains, “the influenza vaccine still provides protection against severe illness, including hospitalization.”
“Public health strongly encourages anyone who has not yet received a flu vaccine this year to get one now, especially before gathering with loved ones during the holidays,” the department said in a statement.
But, according to the scientists, “although mismatched vaccines may still provide protection, enhanced genetic, antigenic and epidemiological monitoring is needed to inform risk assessment and response.” write to Journal of Assn. Medical Microbiology and Infectious Diseases Canada.
Because the vaccine isn't ideal for the latest mutated flu strain, Chin-Hong said giving antiviral drugs like Tamiflu to infected patients could be especially important this year, even for those who are vaccinated. This is especially true for the most vulnerable populations, which include the very young and the very old.
“But that means you need to get diagnosed sooner,” Chin-Hong said. According to the US Centers for Disease Control and Prevention, drugs such as Tamiflu work best if started within one to two days of the onset of flu symptoms.
Home flu testing kits are now available for sale for people who show signs of illness.
Also alarming is how flu rates have increased in other countries.
Australia's flu season arrived earlier this year and was more severe than usual. Royal Australian College of General Practitioners said the country was experiencing a record flu season with more than 410,000 laboratory-confirmed cases, up from the previous record of 365,000 reported last year.
“This is not a record we want to break,” said Dr. Michael Wright, president of the physician group. said.
Hudson noted that this year's flu season in Australia has been “particularly difficult for children.”
Los Angeles County health officials cautioned that Australia's experience is not a reliable predictor of what's happening locally.
“It is difficult to predict what will happen in the United States and Los Angeles because the severity of the flu season depends on many factors, including circulating strains, pre-existing immunity, vaccine use, and the overall health of the population,” the Los Angeles County Department of Public Health said.
The new strain has also brought changes to the situation. As Australia's flu season was winding down, “this new mutation emerged and caused the flu to spread to Japan, the UK and other parts of Europe and Asia,” Chin-Hong said.
Japan reportedly issued a national warning on Friday of a rise in flu cases and hospitalizations, especially among children and the elderly, accompanied by a sharp increase in school and classroom closures. Japanese newspaper Asahi Shimbun. said Children aged 1 to 9 years and adults 80 years and older were among the hardest hit groups.
Taiwan health officials have warned of the possibility of a second flu peak this year. Central News Agency. A peak was already seen in late September and early October – a month earlier than usual – and officials are warning of a rise in flu cases that will begin in December and then peak around the Lunar New Year on Feb. 17.
Taiwanese officials said 95% of patients with severe flu symptoms had not been recently vaccinated.
British health officials released a “flu shot SOS” this month. early wave amazed the nation. The number of flu cases is “already three times higher than last year,” Health Minister Ashley Dalton said in a statement.
In England, apart from the pandemic years, this autumn marked the earliest start of the flu season since 2003-2004, scientists say said in Eurosurveillance magazine.
“We must prepare for another year of new flu cases,” Chin-Hong said.
One major concern is declining flu vaccination rates, a trend seen in both Australia and the United States.
In Australia, only 25.7% of children aged 6 months to 5 years were vaccinated against influenza in 2025, the lowest rate since 2021. Among seniors 65 and older, 60.5% have been vaccinated, the lowest rate since 2020.
Australian health officials are promoting free flu vaccinations for children, which do not require injections but are administered through a nasal spray.
“We have to increase vaccination rates,” Wright said.
In the United States, officials recommend annual flu vaccination for everyone 6 months of age and older. People age 65 and older are eligible for the higher-dose version, and children and adults ages 2 to 49 are eligible to be vaccinated with FluMist nasal spray rather than by needle injection.
This year, officials began allowing people to order FluMist for use. sent by mail them at home.
Besides getting vaccinated, other ways to protect yourself from the flu include washing your hands frequently, avoiding sick people, and wearing a mask in high-risk settings, such as airports and airplanes.
Healthy people at high risk, such as older adults, may be prescribed antiviral drugs such as Tamiflu if another family member has the flu, Chin-Hong said.
Doctors are especially concerned about infants, toddlers, and young children under 5 years of age.
“These are the children who are the most vulnerable if they get any kind of respiratory illness. It could be very bad for them and they could end up getting very sick,” Hudson said.
In the United States, only 49.2% of children had gotten a flu shot at the end of April, down from the 53.4% who had done so at the same point in the previous season, according to preliminary national data. survey results. Both figures are significantly lower final flu vaccination rate for eligible children in the 2019–20 season, which was 63.7%.
Among adults, 46.7% had gotten a flu shot as of the end of April, down slightly from 47.4% at the same time last season, according to preliminary survey results, which are the most recent data available.
“Before the COVID-19 pandemic, influenza vaccination coverage was slowly increasing; coverage declined during and after the pandemic. Influenza vaccination rates have not returned to pre-pandemic levels.” in accordance with CDC.
Vaccine disdain by federal health officials led by skeptical U.S. Health and Human Services Secretary Robert F. Kennedy Jr. has failed to improve immunization rates, health experts say. Kennedy said The New York Times reported Thursday that he personally directed the CDC to change its website and retract its position that vaccines do not cause autism.
Leading health experts and former officials from the Centers for Disease Control and Prevention (CDC) condemned the change. “Extensive scientific evidence shows that vaccines do not cause autism,” Daniel Jernigan, Demetre Daskalakis and Debra Khoury, former senior CDC officials, wrote in their paper. review article in MS NOW.
“The CDC was updated to cause chaos without a scientific basis. Don't trust this agency,” Daskalakis, former director of the CDC's National Center for Immunization and Respiratory Diseases. added on social networks. “This is a national disgrace.”
State health officials in California, Washington, Oregon and Hawaii on Friday called the new claims on the CDC website inaccurate and said there was decades of “high-quality evidence that vaccines are not associated with autism.”
“More than 40 high-quality studies involving more than 5.6 million children found no link between any routine childhood vaccination and autism,” the Los Angeles County Department of Public Health said Friday. “The increase in autism diagnoses reflects improved screening, broader diagnostic criteria and greater awareness, rather than a link to vaccines.”
Hudson said it's important to get science-based information about flu vaccines.
“Vaccines save lives. The flu vaccine, in particular, saves lives,” Hudson said.
