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Needle-Free mRNA Vaccine Shields Mice From COVID-19 and Flu, Study Finds
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In brief
Researchers at Rutgers and institutions in Japan used a high-pressure liquid jet to deliver "naked" mRNA into the skin instead of an injection needle, then added two adjuvants to boost the immune response. In mice, the combination protected against SARS-CoV-2 and influenza A with less inflammation than standard lipid-particle mRNA vaccines, according to a study published October 22, 2026, in the Journal of Clinical Investigation.
A study published October 22, 2026, in the Journal of Clinical Investigation describes a needle-free way to deliver mRNA vaccines that protected mice against the viruses behind COVID-19 and influenza. The work, led by researchers at Rutgers University and partner institutions in Japan, replaces the hypodermic needle with a high-pressure liquid jet and strips away the lipid nanoparticle shell that wraps mRNA in vaccines such as the Pfizer-BioNTech and Moderna COVID-19 shots, according to coverage of the paper by Medical Xpress and News-Medical.
What is new about this delivery method
Conventional mRNA vaccines encase the genetic material in lipid nanoparticles so it survives in the body long enough to reach cells. The Rutgers-led team instead used unencapsulated, or "naked," mRNA and pushed it directly into the skin with a high-pressure liquid jet, a needle-free injection technique. The skin was chosen because it is rich in immune cells, according to News-Medical's summary of the findings.
Senior author Satoshi Uchida, now at the Institute of Science Tokyo, said the goal was to see whether adjuvants — substances that boost an immune response — could compensate for the loss of the lipid carrier. "A combination of adjuvants could markedly improve vaccine efficacy while maintaining a favorable safety profile," Uchida said, as quoted by News-Medical.
Which adjuvants made the difference
The researchers tested adjuvants and found that pairing two of them worked better than either alone: aluminum phosphate, a compound already used in other licensed vaccines, and CpG, a short synthetic DNA molecule that stimulates innate immune receptors. Combining the two with the jet-injected naked mRNA produced stronger protection than using them separately, per the study summary reported by Medical Xpress and News-Medical.
Rutgers New Jersey Medical School researcher Wadih Arap framed the significance of using already-approved components: "What encourages us is that we achieved protective immunity in mice with a delivery device and adjuvant components that have each already been clinically used in human patients," Arap said, according to News-Medical.
Results in mice
After three doses, mice exposed to SARS-CoV-2 or influenza A showed no detectable infectious virus in lung tissue. For the SARS-CoV-2 challenge, lung viral RNA was roughly 24 times lower in mice that received the adjuvant combination than in mice vaccinated without adjuvants. In the influenza experiment, all vaccinated mice survived the subsequent infection, News-Medical reported.
The needle-free, carrier-free approach also triggered less local and systemic inflammation than laboratory lipid-nanoparticle mRNA formulations tested for comparison, according to the same reporting.
| Feature | Needle-free naked mRNA + adjuvants | Standard lipid-nanoparticle mRNA |
|---|---|---|
| Delivery method | High-pressure liquid jet into skin | Needle injection, usually intramuscular |
| mRNA carrier | None (unencapsulated/"naked") | Lipid nanoparticle shell |
| Immune boosting | Aluminum phosphate + CpG adjuvants | Lipid particles act as built-in adjuvant |
| Inflammation observed in mice | Lower local/systemic inflammation | Higher inflammation in comparison tests |
| Protection in mice (3 doses) | No detectable infectious virus; survival in flu challenge | Established protective efficacy in prior vaccines |
| Human testing | None yet | Approved for human use (e.g., COVID-19 vaccines) |
Why researchers are interested in dropping needles and lipid shells
Rutgers Cancer Institute researcher Renata Pasqualini said the result opens new possibilities for vaccine design. "Showing that a carrier-free, needle-free vaccine can be made protective opens a different design space than the one the field has been working in," Pasqualini said, according to News-Medical. Removing the lipid nanoparticle could simplify manufacturing and potentially reduce the reactions some people have to lipid components, while a needle-free jet could make mass vaccination logistics easier.
Limitations and what comes next
The results so far come only from mice. The research team said the approach needs to be tested in larger animals and that suitable human doses still need to be established before any clinical trials in people, according to Medical Xpress and News-Medical. No human safety or efficacy data exist yet for this specific naked-mRNA, jet-injection, dual-adjuvant combination.
The published paper is titled "Jet-injected combinational adjuvants potentiate naked mRNA vaccines for protection against respiratory viral infections in mice," with Nan Qiao listed among the authors, published in the Journal of Clinical Investigation in 2026.
Questions
- What makes this mRNA vaccine 'needle-free'?
- Instead of a hypodermic needle, the vaccine is pushed into the skin using a high-pressure liquid jet, a delivery method described in the Journal of Clinical Investigation study reported by Medical Xpress and News-Medical.
- Does this needle-free vaccine use lipid nanoparticles like current COVID-19 shots?
- No. The researchers used unencapsulated, or 'naked,' mRNA without a lipid nanoparticle shell, relying instead on skin delivery and added adjuvants, according to News-Medical's report on the study.
- What adjuvants were used to boost the immune response?
- The study combined aluminum phosphate with CpG, a short synthetic DNA molecule, finding the pair worked better together than either adjuvant alone, per Medical Xpress and News-Medical.
- Has this needle-free mRNA vaccine been tested in humans?
- Not yet. The results are from mouse experiments only, and researchers say larger-animal studies and human dose-finding work are still needed before clinical trials, according to the reporting on the Journal of Clinical Investigation paper.
- What diseases did the vaccine protect against in the study?
- In mice, three doses of the needle-free vaccine left no detectable infectious virus in the lungs after exposure to SARS-CoV-2, and all vaccinated mice survived a subsequent influenza A infection, News-Medical reported.
Sources
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