A new preclinical study demonstrates that an experimental, needle-free vaccination method can protect mice against the viruses responsible for COVID-19 and influenza while reducing unwanted inflammation. Published on October 20, 2026, in the Journal of Clinical Investigation, the research was conducted by scientists at Rutgers University, the Innovation Center of NanoMedicine, and the Institute of Science in Japan, according to Newswise. By combining a high-pressure liquid jet injector with a targeted pairing of immune-boosting compounds, the research team successfully triggered strong antibody and cellular immune defenses in mouse models without relying on traditional syringe needles or the fat-based particle carriers used in current messenger RNA (mRNA) vaccines.
While the laboratory results mark a notable technical advance in vaccine delivery design, researchers emphasize that the findings are currently limited to early animal models. According to UA.NEWS, the experimental technique must still undergo rigorous evaluation in larger animals to establish appropriate dosing and confirm safety before any human clinical trials can be considered.
Rethinking How mRNA Vaccines Enter the Body
Conventional mRNA vaccines operate by delivering temporary genetic instructions into the body, prompting cells to produce a harmless viral protein that trains the immune system to recognize and fight off future infections. Because mRNA molecules are naturally fragile and degrade quickly on their own, existing commercial vaccines enclose the genetic material inside tiny, fat-based droplets known as lipid nanoparticles. These lipid capsules protect the mRNA and help it slip across cell membranes, though they are also associated with temporary local soreness and broader systemic inflammatory reactions following an injection.
To explore whether vaccines could function without these fat-based carriers, the international research team investigated the delivery of unencapsulated, or "naked," mRNA directly into the skin. Skin tissue is naturally packed with specialized immune cells, making it an attractive target for immunization. Using a needle-free device that fires a high-pressure liquid jet directly into the skin layers, scientists had previously shown that naked mRNA could enter cells, though the resulting immune defense was too weak to provide reliable protection against disease.
Coauthor Renata Pasqualini of Rutgers New Jersey Medical School and the Rutgers Cancer Institute noted in the Newswise report that demonstrating protective immunity with a carrier-free, needle-free vaccine opens up a distinct design space compared to standard approaches in the field.
The Role of Dual Adjuvants in Strengthening Immunity
To overcome the weak immune response typically seen with naked mRNA, the researchers experimented with adding adjuvants—substances regularly included in traditional protein-based vaccines to stimulate a stronger defensive reaction from the immune system. When the team tested individual adjuvants alongside the jet-injected mRNA, the single additives provided minimal benefit, and several actually dampened portions of the immune response.
A breakthrough occurred when the scientists paired two distinct adjuvants together: aluminum phosphate and short DNA molecules known as CpG. Delivering naked mRNA alongside this specific dual-adjuvant combination significantly strengthened both antibody production and T-cell responses in the vaccinated mice. By tracking the biological reaction, the team observed that the combined compounds activated key immune signaling pathways within the skin and the surrounding lymph nodes, demonstrating that precise immune stimulation is required when lipid carriers are removed from the formula.
Senior author Satoshi Uchida of the Institute of Science Tokyo explained in the Newswise release that one of the team's most encouraging findings was seeing how a dual-adjuvant pairing could substantially improve vaccine effectiveness while maintaining a favorable safety profile in animal testing.
Evaluating Viral Protection and Inflammation in Mice
The research team evaluated the boosted, needle-free delivery method in separate mouse challenge experiments targeting SARS-CoV-2 (the virus that causes COVID-19) and the influenza A virus. Mice received a regimen of three vaccine doses before being exposed to the viruses. Following exposure, laboratory analyses showed that infectious virus levels in lung samples from mice given the adjuvant-boosted vaccines fell below the limits of detection for both SARS-CoV-2 and influenza A.
However, the exact nature of the viral and survival measurements differed between the two disease models, as documented by both Newswise and UA.NEWS:
- COVID-19 Experiment Measurements: In the SARS-CoV-2 tests, mice that received the naked mRNA with the dual-adjuvant combination exhibited lung viral RNA levels approximately 24 times lower than mice vaccinated with naked mRNA without adjuvants. This 24-fold reduction reflects a measurement of genetic viral material in mouse lung tissue rather than a human clinical efficacy percentage.
- Influenza A Survival Outcomes: In the influenza experiments, all mice that received the flu vaccine survived the viral challenge regardless of whether adjuvants were included. Because survival was complete across the vaccinated groups, the study could not establish an additional survival advantage specifically attributable to the adjuvant combination in the flu model, even though infectious virus in the lungs was pushed below detection thresholds.
- Inflammation Comparisons: In separate laboratory tests comparing side-effect profiles, the carrier-free jet injection method produced less local skin irritation and lower systemic inflammation in mice than laboratory formulations of mRNA vaccines built with lipid nanoparticles.
What This Means for Patients and Future Vaccination
For the general public, the prospect of a needle-free vaccine that minimizes arm soreness and flu-like systemic side effects is naturally appealing, particularly for individuals who experience needle phobia or sensitivity to current mRNA booster formulations. Removing lipid nanoparticles could also simplify vaccine manufacturing and storage requirements in the future.
Even so, public health guidance and clinical expectations must remain grounded in the realities of drug development. The current findings represent early-stage preclinical mouse research rather than a ready-to-use seasonal shot for humans. Available scientific reporting does not indicate whether the SARS-CoV-2 and influenza mRNAs were mixed into a single combined injection or administered solely in separate testing protocols, nor does it establish how long the immune protection lasts.
Before this needle-free technology can reach medical clinics, researchers must verify whether high-pressure liquid jet injectors can effectively penetrate thicker human skin layers with the same efficiency seen in mice. Extensive testing in larger animal models, precise dose calibration, and multi-phase human clinical trials overseen by regulatory agencies will be required to confirm whether this carrier-free method is safe and protective in people.
Frequently Asked Questions
Were the COVID-19 and flu vaccines given as a single combined shot in this study?
Available summaries of the research confirm that the needle-free platform was tested against both SARS-CoV-2 and influenza A in mouse challenge experiments, but the reports do not specify whether the two mRNAs were mixed into a single combined formulation or administered solely as separate vaccine preparations.
Does a 24-fold reduction in viral RNA mean the vaccine is 24 times more effective in humans?
No. The approximate 24-fold reduction specifically measures the amount of SARS-CoV-2 viral RNA detected in the lung tissue of mice given the adjuvant-boosted vaccine compared to mice given the unboosted naked mRNA vaccine. It is a laboratory tissue measurement in rodents and does not translate to a human clinical efficacy rate.
When might a needle-free mRNA vaccine become available to the public?
There is currently no timeline for public availability. The researchers stated that the technique must first be evaluated in larger animals to determine appropriate dosing and safety profiles before human clinical trials can even begin.
