Scientists have discovered a surprising new way to deliver vaccines: using dental floss to place them in the tiny space between the teeth and gums.
This area, called the junctional epithelium, is a thin layer of tissue that is much more permeable than other parts of the mouth.
In tests with lab animals, this unusual method triggered a strong immune response — especially in mucosal surfaces such as the nose and lungs, which are common entry points for viruses like flu and COVID-19.
Normally, vaccines are given by injection into the arm. This produces antibodies in the blood, which help protect the whole body.
But it doesn’t produce many antibodies on mucosal surfaces — the thin layers that line areas like the respiratory tract, eyes, and mouth. Those surfaces are often the first place viruses land before they can invade deeper into the body.
When vaccines are applied directly to a mucosal surface, the immune system responds both in the bloodstream and in those surface layers. That means the body gains an extra barrier of defense before pathogens even have a chance to get inside.
The junctional epithelium is an especially interesting target for this. Located at the bottom of the gum pocket where teeth meet gums, it naturally allows immune cells to move through to help fight bacteria. Because it is more permeable than most epithelial tissues, it offers a doorway for vaccines to get in and alert the immune system.
In their study, researchers at Texas Tech University and North Carolina State University tested the idea by coating unwaxed dental floss with a flu vaccine.
They flossed the teeth of lab mice, making sure the vaccine touched the junctional epithelium. They then compared the immune responses to mice vaccinated in other ways, such as under the tongue or through the nasal passages.
The flossing method produced much stronger antibody levels on mucosal surfaces than the under-the-tongue method, which is the current best oral vaccination technique. In fact, it gave protection similar to nasal vaccination, which is considered very effective.
But nasal delivery has safety concerns — in rare cases, material placed in the nose could travel to the brain — and it doesn’t work for many vaccine types. The floss-based method avoids these problems.
The team also tested the gum-pocket method with different vaccine types, including protein-based vaccines, inactivated viruses, and mRNA vaccines. In every case, the approach created strong antibody responses both in the bloodstream and on mucosal surfaces. Even eating or drinking right after flossing didn’t reduce its effectiveness in the animal tests.
To see if this might work for people, the researchers gave floss picks coated with harmless fluorescent food dye to 27 volunteers. About 60% of the dye ended up in the gum pockets, suggesting the method could work in real life with a little practice.
If proven effective and safe in humans, this method could make vaccination easier, cheaper, and less intimidating. There would be no needles, and people could potentially administer it themselves. However, it wouldn’t work for babies and toddlers without teeth, and more research is needed to see if gum disease or oral infections would interfere with the process.
This research is exciting because it combines a simple everyday habit — flossing — with cutting-edge vaccine science. By targeting a natural entry point for immune cells, it could boost protection right where pathogens often strike first.
The method also bypasses some of the risks and limitations of nasal vaccination, while being potentially low-cost and needle-free. Still, the idea is in the early stages. The current results are from animal studies and small human tests with dye, not actual vaccines.
Larger human trials will be essential before this approach could be widely used. If it works, gum-pocket vaccination could become a game changer for fighting respiratory viruses and other infections.
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The study is published in Nature Biomedical Engineering.
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