Replacing a traditional needle with a fingernail-sized patch may one day make some immunizations painless and possibly more effective. A study published in Nature earlier this week shows that a patch--a square of "microneedles" that are too short to register a typical shot's sting and that dissolve in the skin--effectively immunized mice against a strain of the flu virus. The researchers have yet to test the patch on humans, and that next step could take a few years; the move from a successful animal trial to a human trial isn't a small feat. Still, many see this patch's promise. As Paul Offit, director of the Vaccine Education Center and chief of infectious diseases at Children's Hospital of Philadelphia, says:
"The caveat is, this needs to be extended to humans.... It's not uncommon for vaccines or vaccine delivery systems to look very promising in experimental animals, then fail in humans. But there is every reason to believe this kind of technology could be applicable to children and adults." [HealthDay News]
If the patch proves successful in human studies, here are some reasons it might quickly catch on. Less Packaging Traditional flu immunization shots deliver vaccines via metal, hypodermic needles. The leftover? A contaminated needle that goes straight to the biohazard bin. Researchers have designed this patch's microneedles to disappear after application. They are made from a "bicompatible polymer" that holds the vaccine directly. After immunization, the needles dissolve into the skin itself as they deliver the vaccine, leaving only a watersoluble backing. Explains study coauthor Richard Compans:
“With respect to [the previous] vaccine delivery, we worked with solid metal needles.... The current technology is different because the vaccine is contained in the needle itself, and there is no needle left after the process.” [Tech News Daily]
Less Pain As their name implies, microneedles are short--shorter than .03 inches each. That's too short to trigger the pain associated with a traditional shot. The patch has a grid of 100 of the tiny needles as opposed to one large metal one.
Each microneedle is 650 microns long, about as tall as 10 human hairs stacked on top of each other.... They are arrayed in a grid-like pattern on a patch that's easy to stick on your arm. [Los Angeles Times]
More Protection There may be other benefits from a shot not going as deep. The study tested three groups of mice: one given no flu vaccine, one given a flu vaccine in the traditional way, and one given the vaccine via the microneedle patch. Infecting the mice with the flu virus thirty days after immunization, both the mice vaccinated traditionally and with the patch successfully fought off the virus. To test how long the vaccine worked, the researchers then vaccinated a different three sets of mice. Three months later, the mice vaccinated with the patch actually performed better than the needle-immunized mice--more easily clearing the virus from their lungs. Researchers suspect that the reason may be skin cells' different immune reaction to virus attackers, which they encounter more often than muscle cells do (where traditional flu shots deliver the vaccine).
Skin, it seems, may trigger the immune system better than muscle, according to Richard Compans, professor of microbiology and immunology at Emory University School of Medicine: "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." [CNET]
Less Postage? Although traditional delivery systems for standard vaccines are working in many places, the researchers think that a patch vaccine might allow a more rapid and effective response to unexpected outbreaks. Instead of asking people at risk to go to a central location like a flu clinic, doctors could mail them a do-it-yourself patch.
[Coauthor Mark R.] Prausnitz says it'd be much easier if people could either vaccinate themselves or have someone less skilled vaccinate them instead of requiring a doctor or nurse. If the patches are one day approved by the FDA, Prausnitz envisions people ordering patches through the mail or at their local pharmacies."The technology is ready to take the next step into humans," says Prausnitz. "Our main barrier is getting funding." [NPR]
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Image: flickr / El Alvi