A fear of needles is one reason why some people delay or avoid vaccines. Research suggests this fear is common: A 2019 meta analysis found that 20 to 30 percent of adults ages 20 to 40 fear needles. In a 2021 U.S. survey, 52 percent of people who hadn’t yet gotten their first dose of the COVID-19 vaccine reported a moderate to severe fear of needles.
But there’s good news for people with needle phobia: One needle-free option is already available—FluMist, a nasal spray flu vaccine approved for use at home in some states for people ages 2 to 49. (You may also be able to get FluMist at a pharmacy.) And now, a recent study suggests that vaccines delivered using dental floss may be a possibility one day. Researchers found that a floss-based flu vaccine triggered a strong immune response in mice. While the research is still in its early stages and has not been tested in humans, it raises the possibility of a future vaccine option that doesn’t require a needle.
To better understand how this might work, we spoke to Rohan Ingrole, PhD, a chemical engineer and co-author of the study, which he wrote while earning his doctorate at Texas Tech University.
Why use dental floss for vaccines?
“Millions of people use floss when something is stuck between their teeth, so we tried to repurpose the floss,” Ingrole says. “Instead of trying to remove something that is stuck, [we thought,] ‘Could we deliver something by coating it on the surface of the floss?’”
Beyond familiarity, floss has other potential advantages. It doesn’t have to be stored cold (like regular vaccines do), making it easy to transport. It could be used at home, without a health care provider or trip to a pharmacy or clinic. And importantly, it could deliver a vaccine through the mouth, one of the main entry points for many viruses and other pathogens.
That’s because of a part of the mouth called the gingival sulcus, the narrow space where the tooth meets with the gum. Within that area is a layer of tissue called the junctional epithelium, which absorbs substances more easily than skin does.
“For example, your skin is not highly permeable: If you put a water droplet, it will stay on the surface for a prolonged period of time,” Ingrole adds. “But here, the cells are different: If you put something into the cavity…it will easily take up anything and everything that could be delivered.”
Another advantage, Ingrole explains, is the role of the mouth in developing immunity. Many viruses enter through your nose and your mouth (known as mucosal sites), so a vaccine delivered through the mouth could provide protective proteins (antibodies) directly to that area. “When you get an injection for a vaccine, you don’t get mucosal immunity; you just get systemic immunity,” Ingrole adds. “What that means is there are antibodies in your blood but not at those mucosal sites—but imagine if you had antibodies at the port of entry.”
What did the study test, and what did it find?
In the early-stage study, published in July, scientists coated dental floss with a flu vaccine molecule and used it to floss the teeth of healthy mice. The mice developed both systemic immunity and mucosal immunity, and the vaccine helped protect them against flu infection.
To explore whether this approach could one day work in people, the researchers also ran a small feasibility test. They coated floss picks with a fluorescent food dye and asked human volunteers to floss their teeth. The dye showed that the floss reached the gingival sulcus, suggesting the method could physically deliver a vaccine to the right location in the mouth.
How might floss-based vaccines work in the future?
Ingrole and his team envision a floss-based vaccine that could be picked up at a pharmacy and used at home. The floss—or possibly a floss pick—would be coated with a vaccine and come with instructions for use. As a person flosses between their teeth, the vaccine would reach the junctional epithelium, where it would help trigger an immune response against the pathogen it targets, like the flu virus.
When can people expect to see floss-based vaccines?
Floss-based vaccines are still in very early stages, Ingrole says. The next step would be testing them in what researchers call “higher animal models,” such as pigs, whose oral anatomy is more similar to that of humans.
The safety of a floss-based vaccine also needs more research: “When we deliver something into the gingival sulcus,” he says, “we want to make sure it does not create more problems.” Ingrole also notes that the study was done only in healthy mice, so scientists need to find out more about “the effect of disease [or the] state of gums.”
Eventually, human clinical trials would be required. “Going from a lab-based animal model to humans, that’s the bridge we need to cross,” Ingrole says.