Scientists are working on a universal flu vaccine that could protect people from many influenza strains with a single shot. Unlike current vaccines, this new approach could last longer and reduce the need for yearly flu shots.
Every year, about one billion people worldwide catch the flu. The illness often causes fever, fatigue, headaches, and coughing. It can keep people sick for a week or longer.
According to the World Health Organization, influenza leads to 290,000 to 650,000 deaths each year. Because of this risk, health experts encourage people to get vaccinated annually.
Why Flu Vaccines Change Every Year
The flu virus constantly changes. Scientists call this process mutation.
Professor Nicholas Heaton from Duke University School of Medicine explains that influenza can quickly evolve. These changes help the virus avoid the body’s immune defenses.
Seasonal flu vaccines work well, but they are not perfect. Their effectiveness usually reaches around 60%. In some seasons, protection drops if the vaccine does not match the circulating virus.
This is why people must get a new flu shot every year.
The Goal of a Universal Flu Vaccine
Researchers want to develop a vaccine that protects against many strains of influenza.
A universal flu vaccine would aim to:
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Protect against multiple flu strains
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Provide long-lasting immunity
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Reduce the need for annual vaccinations
Scientists around the world are studying different ways to achieve this goal.
Currently, about a dozen vaccine candidates are in clinical trials. Many other projects remain in early research stages.
Research scientist Julie Ostrowsky from the University of Minnesota Center for Infectious Disease Research and Policy says the field includes many promising ideas. However, she notes that developing such a vaccine is complex and will take time.
Why Influenza Is Hard to Control
Influenza is not just one virus. Instead, it includes many viruses that spread between humans and animals.
Two proteins on the virus surface play a major role in infection:
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Haemagglutinin
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Neuraminidase
These proteins help the virus enter and exit human cells. When someone gets infected, the immune system creates antibodies that target them.
However, these proteins change frequently.
Scientists have identified:
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18 types of haemagglutinin
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11 types of neuraminidase
Different combinations create flu subtypes such as H1N1 and H3N2.
Over time, small mutations build up in the virus. Eventually, these changes help influenza escape immune protection from previous infections or vaccines.
Predicting Future Flu Strains
Each year, experts try to predict which flu strains will spread during the upcoming season.
The World Health Organization gathers scientists from around the world to review global influenza data. They analyze how the virus spreads and evolves.
In February, experts recommend vaccines for the Northern Hemisphere. Flu season there usually begins around October.
In September, they make recommendations for the Southern Hemisphere, where flu season starts around April.
Despite this effort, predictions can miss new variants.
For example, during the 2025–2026 flu season, outbreaks appeared from an H3N2 subclade K virus. This variant had not yet emerged when experts made vaccine recommendations earlier that year.
The Future of Flu Protection
Scientists continue to search for stable parts of the influenza virus that rarely change. Targeting these areas could allow a single vaccine to protect against many flu strains.
If successful, a universal flu vaccine could transform how the world fights influenza. It could reduce global illness, save lives, and make yearly flu shots unnecessary.
