Nasal Spray Vaccine Blocks Bird Flu in Lab Animals

A simple spray up the nose could be our best defense against the bird flu virus that's been quietly spreading from wild birds to dairy cows to humans across America.

Researchers at Washington University School of Medicine in St. Louis developed a nasal vaccine that stopped H5N1 bird flu infections in their tracks when tested in hamsters and mice. The protection was nearly perfect, even when animals received low vaccine doses but faced high virus exposure.

The timing matters. Since bird flu jumped into U.S. dairy cows last year, more than 70 Americans have caught the virus, including two who died. Every animal infection gives the virus another chance to evolve into something that spreads easily between people.

"This particular version of bird flu has been around for some time, but the unique and totally unexpected event where it jumped across species into dairy cows was a clear sign that we should prepare," said Dr. Jacco Boon, who led the study with colleagues Dr. Michael Diamond and Dr. David Curiel.

The nasal approach beats traditional flu shots in a crucial way. By delivering protection directly where infections start, in the nose and upper airways, it blocks the virus before it can take hold. Regular flu shots mostly prevent severe disease but don't stop nose and throat infections as well.

The research team built their vaccine using the same technology behind a COVID-19 nasal vaccine already used in India since 2022. They designed a custom antigen from H5N1 proteins representing strains that have infected humans, then packaged it into a harmless adenovirus that carries the vaccine into cells.

One major concern was whether people's existing immunity from years of flu shots would interfere with the new vaccine. It didn't. The nasal vaccine protected animals strongly regardless of prior flu exposure, which means it should work for nearly everyone except young children getting their first flu vaccine.

Why This Inspires

This breakthrough shows how scientists are staying one step ahead of potential pandemics instead of scrambling to catch up. The same platform that created COVID nasal vaccines can now be adapted quickly for bird flu and future respiratory threats.

The research, published in Cell Reports Medicine, represents years of collaborative work that's already approved for human testing in the United States. What started as pandemic preparation for COVID has become a versatile tool against multiple viral threats.

Next, the team will test the vaccine in animals with immune systems closer to humans and continue refining the formula to maximize protection. The goal is a vaccine ready to deploy if bird flu ever gains the ability to spread easily among people.

A nose spray that prevents infection entirely could break the transmission chain before a pandemic starts.