Scientists in the US who developed a skin patch that uses hundreds of microscopic dissolvable needles to deliver vaccine into the body have shown it works on animals, perhaps even better than the traditional injection method; they envisage that one day this approach could reduce the cost and administration of mass vaccination, for instance during flu epidemics, because people could receive the patches by post or get them from a pharmacy and apply them to themselves at home.
Researchers from Emory University and the Georgia Institute of Technology (Georgia Tech) in Atlanta, Georgia, reported how they used the dissolving microneedle patches to show immunization benefits in lab mice in a paper that went online in Nature Medicine on the 18th of July.
The search to find a way to deliver vaccine more cheaply with less burden on the logistics of the health system, while at the same time reducing the risk posed by hypodermic needles and the cost of safe disposal of “sharps”, has been challenging researchers for some time.
Skin patches that deliver medication via the skin, like the nicotine ones used by people trying to quit smoking, are not effective for vaccines, so researchers have been looking at the possibility of microneedles, where vanishingly small needles carry the vaccine straight into body fluids.
Co-author Dr Mark Prausnitz, a professor in the Georgia Tech School of Chemical and Biomolecular Engineering, told the media that:
“In this study, we have shown that a dissolving microneedle patch can vaccinate against influenza at least as well, and probably better than, a traditional hypodermic needle.”
His colleague and co-author Dr Richard Compans, professor of microbiology and immunology at Emory University School of Medicine, said:
“The skin is a particularly attractive site for immunization because it contains an abundance of the types of cells that are important in generating immune responses to vaccines.”
For this mouse study, which was funded by the National Institutes of Health (NIH), Prausnitz, Compans and colleagues used a patch containing a tiny array of 100 vanishingly small microneedles each 650 micrometers long (human hair is about 100 micrometers thick) .
They started with three groups of mice: they gave one group the flu vaccine using traditional hypodermic needles injected into muscle, they gave flu vaccine to the second group by applying it via dissolving microneedle skin patches, and they also applied dissolving microneedle skin patches to a third group, the controls, but in their case they did not put any vaccine in the patches.
They then exposed all three groups of mice to a lethal dose of flu virus 30 days later.
The results showed that the two groups of mice that had received the vaccine (one via intramuscular injection, the other via the microneedle skin patches) stayed healthy while the mice in the control group got sick with the flu and died.
In the meantime, the researchers had also run a parallel experiment with another two groups of vaccinated mice, one vaccinated using injection the other with microneedle skin patches.
When they exposed these mice to flu virus three months after vaccination, the microneedle skin patch group showed a better imuune response: their antibody response was more “robust” and they were better able to clear the virus from their lungs than the groups that had been vaccinated by hypodermic needle.
The researchers concluded that:
“These results suggest that dissolving microneedle patches can provide a new technology for simpler and safer vaccination with improved immunogenicity that could facilitate increased vaccination coverage.”
Dr Ioanna Skountzou, an Emory University assistant professor, said that another advantage of using microneedles is that the vaccine can be in a dry formulation, which means it is more stable and easier to store and distribute.
Also, once the patch is pressed into place, the microneedles quickly dissolve in bodily fluids and leave only the water-soluble backing, which can be thrown away.
As lead author Sean Sullivan, also from Georgia Tech, explained:
“Because the microneedles on the patch dissolve away into the skin, there would be no dangerous sharp needles left over.”
He said they could imagine people receiving the microneedle patch in the mail or getting it from a pharmacy and then applying it at home.
The microneedle array that Sullivan and colleagues used in this study was made from poly-vinyl pyrrolidone, a polymer that has already been tested and found safe to use inside the body.
To make the array, they freezed dried the vaccine and mixed it with a monomer form of the base material, put it into the needle molds then converted the compound into the polymer form by shining UV light on the array at room temperature.
While this study only examined the delivery of flu vaccine there is no reason, the researchers suggest there is no reason why it couldn’t work for other vaccines.
For instance in many parts of the world, inadequate health systems often mean hypodermic needles are re-used which helps spread diseases like HIV and hepatitis B. Dissolving microneedle patches would do away with re-use risk, and could also be given out by people with less training.
Prausnitz said once mass produced, the cost of delivering vaccine via microneedle patches should be about the same as the cost of using conventional needles and syringes, and the overall cost of immunization programs could even come down because costs of training and waste and disposal would be lower.
However, the researchers stressed there is still a way to go before we can hope to see such a scenario. For example, clinical studies have not yet been done to test the safety and effectiveness of vaccine delivery using microneedle skin patches in humans, and we still don’t fully understand why the microneedle system appears to give better immunity than the injections.
“Dissolving polymer microneedle patches for influenza vaccination.”
Sean P Sullivan, Dimitrios G Koutsonanos, Maria del Pilar Martin, Jeong Woo Lee, Vladimir Zarnitsyn, Seong-O Choi, Niren Murthy, Richard W Compans, Ioanna Skountzou, Mark R Prausnitz.
DOI:10.1038/nm.2182
Additional source: Georgia Tech.
Written by: Catharine Paddock, PhD