Lab study shows needle-free mRNA vaccine protects against COVID and flu
· Medical Xpressedited by Sadie Harley, reviewed by Robert Egan
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A needle-free vaccination method protected mice against the viruses that cause COVID-19 and flu, offering a possible new way to deliver mRNA vaccines while limiting unwanted inflammation.
The Journal of Clinical Investigation study by researchers at Rutgers and Japanese institutions tests experimental improvements to mRNA vaccine delivery. The approach combines a high-pressure liquid jet that delivers mRNA into the skin with two substances that strengthen the immune response.
"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," said co-author Renata Pasqualini of Rutgers New Jersey Medical School and Rutgers Cancer Institute, New Jersey's only National Cancer Institute-designated comprehensive cancer center, together with RWJBarnabas Health.
Delivering mRNA without lipid capsules
mRNA vaccines give cells temporary instructions to make a protein that trains the immune system to recognize a threat. In existing vaccines, tiny fat-based particles form capsules around the fragile mRNA, helping it enter cells and stimulate immunity.
The researchers explored another approach: delivering unencapsulated, or "naked," mRNA into the skin, which is rich in immune cells. Earlier work showed that jet injection could effectively deliver mRNA, but the resulting immune response was weak.
Two adjuvants outperform either alone
Researchers tried to bolster the effect by adding adjuvants, substances that enhance conventional vaccines. Unfortunately, these adjuvants offered little benefit when used individually with the mRNA. Some actually weakened parts of the response.
However, combining two different adjuvants—aluminum phosphate and short DNA molecules called CpG—boosted both antibody and cellular responses.
The researchers traced part of the benefit to immune signals activated in the skin and nearby lymph nodes. Their findings suggest that selecting the right immune stimulation and delivering mRNA into cells are essential to making this method work.
"One of the most exciting discoveries in developing our carrier-free mRNA vaccines was that a combination of adjuvants could markedly improve vaccine efficacy while maintaining a favorable safety profile in our animal studies," said senior author Satoshi Uchida of the Institute of Science Tokyo.
Protection in mice needs broader testing
After three doses, infectious virus was below detection limits in lung samples from mice given the boosted vaccines and later exposed to SARS-CoV-2 or influenza A. In the COVID-19 experiment, lung viral RNA was about 24 times lower than after vaccination without the adjuvants. Both flu vaccine groups survived, so no additional survival benefit from the boosters was established.
Separate experiments found less local and systemic inflammation than with laboratory lipid-particle formulations of the mRNA vaccine.
Despite its success in mice, the new approach still needs testing in larger animals before human trials, including establishing suitable doses.
"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," said co-author Wadih Arap of Rutgers New Jersey Medical School and Rutgers Cancer Institute.
Publication details
Nan Qiao et al., Jet-injected combinational adjuvants potentiate naked mRNA vaccines for protection against respiratory viral infections in mice, Journal of Clinical Investigation (2026). DOI: 10.1172/jci204021
Journal information: Journal of Clinical Investigation
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Infectious diseasesClinical pharmacology Provided by Rutgers University Who's behind this story?
Sadie Harley
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Citation: Lab study shows needle-free mRNA vaccine protects against COVID and flu (2026, October 22) retrieved 23 October 2026 from https://medicalxpress.com/news/2026-10-lab-needle-free-mrna-vaccine.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.