Flu Vaccine: It’s Not Too Late to Get a Shot, Experts Say
Influenza reached the US west coast about two and a half months earlier than normal this season. The CDC counts 16,000 flu hospitalizations so far, and experts say vaccination still protects against severe illness even though this year's shot is a weaker match.
Influenza has reached the US west coast about two and a half months earlier than normal this season, according to Dr Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota. Experts say it's not too late to get a flu shot, even though this year's vaccine is a weaker match for the dominant virus.
It is the earliest start since the 2010 season, Osterholm said. The US Centers for Disease Control and Prevention (CDC) still rates overall flu activity as low, with 16,000 recorded flu-related hospitalizations so far. It expects infections to keep rising in the coming weeks as the virus spreads through the Midwest and East Coast.
Dr Amesh Adalja, an infectious disease specialist at the Johns Hopkins Center for Health Security, said travel patterns may have played a part. But "there’s not a completely ironclad explanation for why this has occurred," he said.
A mutated H1N1 strain
This year's dominant strain is an H1N1 virus carrying a mutation known as G155E. Adalja said there is no evidence the mutation makes the virus more likely to cause severe illness. It does resemble features of H1N1 strains that circulated before 2009.
Early research suggests teens and young adults under 25 "have less immunity" to this strain, Adalja said. The virus may be "more able to get around some of the immunity that people have from prior infections and prior vaccinations," he said.
One US pediatric flu death has been reported this season, involving an elementary-aged child from outside the Denver metro area. An estimated 24,000 people, 198 of them children, died of flu-related illness in the 2025-26 season.
Dr Alex L Greninger, head of the division of infectious disease diagnostics at the University of Washington, said outcomes depend more on the individual than the virus. People with diminished cardio respiratory capacity are one example. "If you’ve recently had heart disease, when the flu comes it can push you over the edge in terms of heart and lung function," he said.
Why the vaccine is a weaker match
Every February, the World Health Organization (WHO) convenes experts to forecast which flu variants will dominate the northern hemisphere the following winter. This year's forecast missed. "This particular variant really emerged after we already had chosen what was in the vaccine," Osterholm said.
Adalja said the process relies on slow, old technology. "We make vaccines for flu the same way we made them in the 1940s; we use very old technologies that require a long lead time," he said.
Osterholm said the question is not whether the vaccine works, but that it is less protective. He compared being vaccinated to "having your seatbelt attached against the flu. It protects you against severe disease, hospitalization, and death."
Adalja said the mismatch has nothing to do with the US leaving the WHO. The CDC still took part in the strain selection process, he said, and the strains used in the United States are identical to those given in Canada and Mexico.
This is also the first year the public can get an mRNA-based flu vaccine, made by Moderna and called mFlusiva. It is recommended for adults 50 and older, the group at highest risk from flu.
