Floss may replace needles soon: breakthrough in vaccine delivery

Flossing might one day do more than just prevent gum disease—it could save lives.

While oral mucosal sites, such as the sublingual and buccal areas, have long been explored for needle-free vaccine delivery, they pose challenges due to their protective barriers. However, the gingival sulcus, particularly the junctional epithelium, stands out for its leaky characteristics. This distinct anatomical feature is precisely what makes floss-based vaccination so promising.

From gum disease to immunity

The idea originated with Harvinder Gill, a nanomedicine expert at North Carolina State University. While reading about periodontal disease, he discovered research describing the gingival sulcus as a site of high permeability. That observation sparked the question: could this property be harnessed for vaccine delivery?

In collaboration with Rohan Ingrole from Texas Tech University, Gill and his team undertook what can only be described as a challenging experiment—vaccinating mice with dental floss.

By coating floss with fluorescent proteins and threading it through the gingival sulcus of anaesthetised mice, they successfully delivered various agents, including proteins, inactivated virus particles, mRNA, and immunogenic nanoparticles.

The immune response was striking. Not only did vaccinated mice exhibit elevated levels of antibodies in the lungs, nose, and spleen, but their bone marrow also showed the presence of active antibody-secreting cells. Immune activation extended beyond local lymph nodes to systemic organs, such as the spleen and lungs. Remarkably, the immune response persisted for over two months and was unaffected by age, food, and fluid intake.

Flossing for protection

The true test came with a live virus challenge. Mice vaccinated using floss with inactivated influenza virus survived exposure to lethal flu strains, whereas their unvaccinated counterparts did not. The immunological profile closely mirrored that of intranasal vaccines, such as FluMist, suggesting that flossing may be a viable mucosal immunisation route.

Human feasibility was also tested. In a small trial of 27 volunteers, dental picks coated with fluorescent dye were used to floss the gums. Around 60% of the dye reached the gingival sulcus, indicating effective delivery. Notably, most participants expressed openness to the method and even preferred it over traditional injections.

What lies ahead?

Although this technique is still in its early stages, it shows enormous potential for revolutionising vaccination strategies, particularly in settings with limited access to syringes or cold chain infrastructure. Experts, such as Prof. William Giannobile at Harvard, have praised the ingenuity of the approach, although they urge caution until larger clinical trials are conducted. Particularly, there is a need to explore the impact of variable gum health, given the global prevalence of periodontal disease.

For dentistry, the implications are exciting. Imagine patients receiving vaccinations as part of routine dental visits—a seamless integration of preventive oral and systemic health.
This floss-based method may be the start of a new era in needle-free immunisation. As researchers continue to refine the technology, the dental profession could be poised to play a pivotal role in global health beyond the mouth.

References:

1. Ingrole, R.S.J., Shakya, A.K., Joshi, G. et al. Floss-based vaccination targets the gingival sulcus for mucosal and systemic immunization. Nat. Biomed. Eng (2025). https://doi.org/10.1038/s41551-025-01451-3
2. Engineers transform dental floss into needle-free vaccine
3. A vaccine coated floss as a novel vaccination platform
4. Floss: a novel method for oral mucosal vaccination

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