Flu cases are already increasing across the US. Is this year’s flu shot effective?
Por Julia Musto — – World RSS Feed
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Flu cases are already increasing across the US. Is this year’s flu shot effective?
CDC data shows a 30 percent increase in positive tests for the flu over the last week
Julia Musto in New York Monday 19 October 2026 15:33 BST
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With flu season ramping up earlier than is typical this year, many are left to wonder if this year’s flu shot is effective.
The vaccines usually target the primary strains of the virus spreading in a given year – and this year is no exception. This vaccine is designed to fight the H1N1 swine flu and the B/Victoria virus, as well as subclade K, a variant of H3N2 influenza that also spread last year.
Early evidence suggests this year’s shot is a good match against the variant, but less is known about the vaccine’s effectiveness against H1N1, Scott Hensley, a professor of microbiology at the University of Pennsylvania, told NBC News on Friday.
“That third component, we don’t really know at this point,” he said.
open image in galleryEven if protection isn’t perfect, the vaccine still helps to prevent severe illness and death. Flu results in between 9.4-51 million illnesses a year and some 6,300-52,000 deaths, according to the Centers for Disease Control and Prevention.
H1N1 is driving the most illnesses this season, according to the agency’s latest data.
The number of positive tests reported in the last week is 5 percent, which is around a 30 percent increase from the prior week’s data.
The flu season generally runs from September or October and extends into April or May. That’s why it’s never too late to get a flu shot.
The flu shot works by triggering the development of protective antibodies in the immune system about two weeks after vaccination. These antibodies protect against the three seasonal viruses.
The new mRNA flu shots provide even more protection, medical researchers say. They can also be manufactured faster than traditional flu shots.
open image in galleryStill, vaccination rates have fallen in recent years, despite widening availability. In the 2024-2025 season – the most recent year reported by the CDC – 41.9 percent of adults were vaccinated against the flu, the lowest rate in seven seasons.
Vaccine hesitancy and misinformation about the virus and vaccine have played a role, according to experts, including regarding how severe an infection can be.
“It’s not just a cold,” Dr. Ryan Stanton, president-elect of the American College of Emergency Physicians, said in a recent news briefing, according to AARP. “There is just a cold out there. I still don’t want to have that one either. But a lot of these [respiratory viruses] are much, much more serious.”
Doctors say people should get their shots now for protection in colder months when flu activity is elevated.
“The protection of the flu vaccine wanes with time, and you will have the most effective protection from the vaccine for about three to four months after receiving it,” Dr. Victoria Weston, the associate chief medical officer for immediate care at Northwestern Medicine, told Parade in September.
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USCenters for Disease Control and PreventionFluInfluenzaVaccineVaccination
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