Shots are a pain, even beyond the needle prick.
That's because transporting and storing vaccinations and other substances delivered via injection can be costly and time-consuming, as can training medical workers to give them. Following all of those steps can make the difference, for example, between a population that's inoculated against polio and one that's not.
One way around that problem: Deliver the vaccine not through single needles but through 100 microscopic needles at once. Also make sure those needles attach to a small skin patch that's easier to transport, store and apply.
The patches also could ease doctor's-office fears for people who face frequent pokes.
One patch, under development by the Georgia Institute of Technology, measures a bit smaller than a square centimeter (about the size of a key on a typical computer keyboard). The underside is lined with 100 tiny needles — each a fraction of a millimeter long — made of polymer, sugar and vaccine. When the patch is applied, the needles pierce the skin's top layers and dissolve, releasing the vaccine within minutes.
A microneedle patch like this could be briefly applied to an arm. The needles would dissolve into the skin and carry the vaccine with them. Gary Meek/Georgia Institute of Technology
While the skin offers easy access, it's also a strong defensive system.
“We have to make very tiny needles to break that barrier,” says Jeong Woo Lee, an engineer who's among the Georgia Tech researchers working on the microneedle patches.
Lee said his lab, led by Georgia Tech professor Mark R. Prausnitz, has tested patches loaded with polio, measles, rubella, flu and rotavirus vaccines, with each type of patch producing a strong immune response. They also have experimented with human growth hormone patches. They've experimented with the latter, Lee says, because most patients who take the hormone are kids who “really hate to be injected by the long needles, because it's very painful and visually very scary.”
Along with the logistical benefits, scientists are particularly interested in using microneedle patches to deliver vaccines because of their potential to create a stronger immunological response than people get from shots, Lee says. Microneedles target certain cells — they're called Langerhans cells — that send out immune cells to gather information about invaders, such as viruses. While these immunity-promoting Langerhans cells abound in the skin, they're sparse in the muscles where traditional shots are delivered.
Patching Up Polio
Lee and others in the Georgia Tech lab are testing a polio-vaccine patch, using $2.5 million in grants they got in a partnership with a commercial company, Micron Biomedical, from the Bill & Melinda Gates Foundation.
While most organic molecules used in vaccines wouldn't survive the gastrointestinal tract, oral polio vaccine works and is relatively easy to deliver. The problem, Lee says, is that it's made with live virus, which in rare cases can mutate into a virulent form that infects people. But vaccine made with inactivated virus — without the potential to mutate — has to be administered via long needles. And those are accompanied by all those old challenges: high cost, pain, the need for medically trained personnel and cold storage.
Meanwhile, more than 20 countries have suffered polio outbreaks since 2008, according to the Gates Foundation.
Georgia Tech's patch uses inactivated virus but doesn't require trained personnel, making it easier to vaccinate more people in developing countries, the university says.
The Georgia Tech lab is also working with the Centers for Disease Control and Prevention to develop a microneedle patch containing measles vaccine.
And similar microneedle skin products are in the works by other companies, if they're not already available, to deliver medications.
3M, for example, is looking for partners to produce microneedle patches. It says roughly 10 percent of the population avoids injectable drugs due to a fear of needles. Valeritas, which makes products for people with Type 2 diabetes, calls its Micro-Trans patch “extremely comfortable.”
Lee, at Georgia Tech, said a pain study of people allowed to apply the patches themselves found that while they felt the microneedles, they didn't hurt.