Scientists say they may be able to create a universal flu vaccine that can provide broad protection against various influenza strains, including those that could cause future pandemics. Findings from the study are published in mBio.

Normally, the vaccine changes yearly to match the specific strains that are circulating. If the vaccine is even a bit different to the predicted target virus, it may not offer much protection. Researchers from the National Institute of Allergy and Infectious Diseases (NIAID) used a virus-like particle vaccine cocktail that expressed various different subtypes of a key surface protein of the influenza virus: hemagglutinin H1, H3, H5, and H7. They hypothesized that the presence of different viral proteins would stimulate the cross-protective immunity that would give broader protection against multiple subtypes.

The H1 and H3 subtypes were chosen because they have been major causes of human seasonal flu outbreaks sine 1918; the H5 and H7 subtypes were chosen because they have been the cause of recent avian flu outbreaks and have pandemic potential.

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Among mice given the investigational cocktail vaccine, 95% of them were protected against a lethal challenge of eight different influenza strains expressing seven different influenza A subtypes vs. only 5% of mice who were given mock vaccinations. Almost all the mice that were vaccinated survived, even after being challenged with viruses that expressed hemagglutinin subtypes not included in the vaccine such as H2, H6, H10, and H11. Further experiments demonstrated that the vaccine was durable, effective for ≥6 months, and was effective in older mice.

Study findings suggest a possible basis for a future pre-pandemic vaccine. Researchers concluded that the positive findings may serve as a practical strategy to develop a vaccine with broad protection.

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