Your next flu shot? It might come between your teeth.

Through a study that could transform the way vaccines are delivered, scientists have discovered that flossing between your teeth may one day do more than clean your gums—it could help immunise you.

Published in Nature Biomedical Engineering, the study titled "Floss-based vaccination targets the gingival sulcus for mucosal and systemic immunisation" unveils a groundbreaking technique developed by researchers from North Carolina State University, Texas Tech University, and collaborating institutions. The team successfully used dental floss to deliver vaccines through gum tissue, triggering a powerful immune response at critical infection entry points—the mouth, nose, and lungs.

The technique targets the junctional epithelium—a uniquely permeable layer of gum tissue located between the teeth and gums. Unlike most epithelial barriers in the body, which are designed to keep pathogens out, this gum tissue naturally allows immune cells to move in and out, making it an ideal point of entry for vaccine delivery.

“Because the junctional epithelium is more permeable than other epithelial tissues—and is a mucosal layer—it presents a unique opportunity to introduce vaccines in a way that stimulates enhanced antibody production across the body’s mucosal surfaces,” explained Dr. Harvinder Singh Gill, senior author of the study and professor of nanomedicine at NC State.

In lab tests, researchers applied a flu vaccine to unwaxed dental floss and used it to floss the gums of mice. The immune response was robust, more effective than existing oral vaccines and on par with nasal vaccines, but without the associated risks, such as the possibility of the vaccine reaching the brain.

They also tested the method with other vaccine types, including mRNA, inactivated virus, and protein-based vaccines—all of which triggered strong antibody responses both in the bloodstream and at mucosal sites like the lungs and nose.

Unlike traditional injections, this technique delivers antibodies right to the frontlines, where many viruses first strike.

“This improves the body’s ability to prevent infection because there is an extra line of defence before a pathogen even enters the body,” said Gill.

To explore whether this approach could work in people, the research team conducted a small pilot test with 27 volunteers. Using floss picks coated with fluorescent dye (in place of a vaccine), participants attempted to apply the substance into their gum pockets. The results were encouraging: about 60 per cent of the dye reached the junctional epithelium, suggesting that floss picks could be a viable vaccine delivery tool.

While the idea of self-administered vaccines through flossing may sound futuristic, researchers believe the method has real-world potential, especially in addressing vaccine hesitancy and improving access in low-resource settings.

“It’s easy to administer, doesn’t involve needles, and should be comparable in price to existing methods,” said Gill.

The technique isn’t without challenges. It likely won’t work for infants and toddlers who don’t yet have teeth, and researchers still need to study how it would perform in individuals with gum disease or oral infections. But they remain optimistic.

Gill and his colleagues have also filed a patent for the floss-based vaccination method, signalling their intention to develop the technology further, possibly into clinical trials.