Dental floss delivers vaccines without needles

Imagine getting your next flu shot not through a syringe, but with something as familiar as flossing your teeth.

A new proof-of-concept study led by Harvinder Singh Gill, a professor of nanomedicine at North Carolina State University brings that vision to life.

The team has shown, in mice, that unwaxed dental floss coated with vaccine can be gently threaded between the teeth and gums. This sparks a powerful immune response where pathogens often strike first – the moist linings of the nose, throat, and lungs.

“Mucosal surfaces are important because they are a source of entry for pathogens, such as influenza and COVID,” Gill explained.

“However, if a vaccine is given by injection, antibodies are primarily produced in the bloodstream throughout the body, and relatively few are produced on mucosal surfaces.”

A hidden vaccine gateway

Conventional epithelium – the skin-like tissue that lines much of the body – forms a tight barrier. The junctional epithelium, tucked deep in the gum pocket where a tooth meets the jaw, is different.

Lacking some of the usual protective proteins, it allows immune cells to patrol the area and intercept bacteria that lurk in dental plaque.

“Because the junctional epithelium is more permeable than other epithelial tissues – and is a mucosal layer – it presents a unique opportunity for introducing vaccines to the body in a way that will stimulate enhanced antibody production across the body’s mucosal layers,”  Gill said.

Delivering antigen there, the researchers reasoned, might train the immune system without needles, sprays, or oral drops.

Floss rivals nasal spray

The team compared three ways of vaccinating mice against influenza: flossing the gum pocket, dripping vaccine under the tongue (the current oral-cavity standard), and instilling it in the nose.

The researchers discovered that flossing outperformed the sublingual route and matched the nasal route. This is notable because intranasal vaccination often requires specially formulated antigens and carries a theoretical risk of delivering particles too close to the brain.

“Applying the vaccine via the junctional epithelium produces far superior antibody response on mucosal surfaces than via the oral cavity, which involves placing vaccine under the tongue,” reported first author Rohan Ingrole, who completed the work as a doctoral student in Gill’s lab.

“The flossing technique also provides comparable protection against flu virus as compared to the vaccine being given via the nasal epithelium.”

Safe, even near brain

Researchers say this new approach is extremely promising because the nasal lining blocks absorption, preventing most vaccines from being delivered through the nose.

“Intranasal delivery also has the potential to cause the vaccine to reach the brain, which can pose safety concerns. However, vaccination via the junctional epithelium offers no such risk,” said Ingrole.

Better still, the new approach worked with multiple vaccine types – proteins, inactivated viruses, and even mRNA – each time generating strong antibody levels in blood and mucosal secretions.

Whether mice nibbled food or drank water right after flossing made no difference, suggesting that ordinary eating habits would not blunt effectiveness.

Testing floss on humans

Unwinding floss around tiny mouse incisors is one thing; asking people to maneuver drug-soaked thread is another.

To gauge feasibility, the researchers dipped the filament of commercial floss picks in fluorescent food dye and asked 27 adult volunteers to aim for their gum pockets.

“We found that approximately 60 percent of the dye was deposited in the gum pocket, which suggests that floss picks may be a practical vaccine delivery method to the epithelial junction,” Ingrole said.

The pilot study, while small, hints that ordinary oral-care tools might one day double as do-it-yourself vaccine applicators – no medical training required.

No needles, no stress

Freedom from needles could ease anxieties and speed mass immunization campaigns. “For example, it would be easy to administer, and it addresses concerns many people have about being vaccinated with needles,” Gill noted.

“And we think this technique should be comparable in price to other vaccine delivery techniques.” The method would also bypass cold sprays, which can fail if the antigen cannot cross the nasal barrier.

Limits include toothless toddlers and adults with gum disease or oral infections that may hinder vaccine uptake. The researchers need to refine dosage, ensure consistent coating of floss material, and run larger safety trials. Yet the early data encourage them.

“We’re optimistic about that work and – depending on our findings – may then move toward clinical trials,” Gill said.

Floss vaccines of the future

If future studies confirm the promise, dental-floss vaccination could shift routine immunizations from clinics to bathrooms, adding a simple daily habit to global public health arsenals.

Beyond flu, the group plans to explore vaccines against respiratory viruses and perhaps oral boosters that top up immunity months or years after a primary shot.

By turning a humble hygiene tool into an immune ally, Gill and colleagues have opened an unexpected channel to the body’s frontline defenses. It’s a reminder that innovation can begin with nothing more than a spool of floss and a curious mind.

The study is published in the journal Nature Biomedical Engineering.

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