Researchers have developed a skin patch that could painlessly deliver vaccines through the skin, replacing hypodermic needles. Scientists say the invention could simplify flu immunization programs by allowing patients to administer vaccines themselves.
Unlike a hypodermic needle that injects a vaccine into muscle tissue, the patch contains microscopic needles that painlessly deliver a vaccine into the outer layer of the skin within minutes after being applied. "It takes about 10 minutes for the microneedles to fully dissolve and to release the vaccine," said Mark Prausnitz, a chemical and biomedical engineer at Georgia Institute of Technology in Atlanta, who led a study of the microneedle patch in mice.
Researchers developed a prototype of the vaccine delivery system, a .65 millimeter patch with an array of 100 microneedles carrying a single dose of an influenza vaccine, which they applied to the skin of mice. A second group of mice received the same flu vaccine through a conventional hypodermic needle injection.
A month later, both groups were exposed to the influenza virus. Investigators found that the vaccine patch offered as much protection against the flu as the vaccine administered by injection.
Prausnitz says that there is evidence that the microneedle patch offers better protection against the flu than injected immunizations.
In a different group of animals, researchers found that after three months, the mice that wore the vaccine patch cleared the virus from their lungs more effectively than those that received a shot.
Prausnitz says that there is a reason why inoculation through the skin might be more effective than vaccination by injection. "The body's immune system has sentry cells that exist throughout the body looking for foreign things that have come to the body that require an immune response. The cells that are in the skin are different kinds of cells than ones that are in the muscle. So it is reasonable to expect that the immune response would be different when the vaccine is given to different tissues. We found that it is not only different, but it is better," he said.
Prausnitz says that after the patch is used, it can be thrown away because all of the microscopic needles dissolve quickly into the fluids in the skin and what remains is only the water-soluble backing.
The researchers are now working on a microneedle patch that can deliver other immunization drugs within a minute or two of being applied to the skin.
In many parts of the world, Prausnitz says, there are not enough hypodermic needles to go around, so needles frequently are reused. That increases the risk of spreading the AIDS virus and other diseases such as hepatitis B. He says there would be no such problem with single-use skin patches.
Prausnitz adds that vaccination campaigns would likely be less costly, particularly in countries where there are few clinics and medical personnel to administer the programs. He says people could simply get the patches at drug dispensaries or through the mail and then apply them to their own skin.
The Georgia Institute of Technology researchers are seeking funds to conduct clinical trials as soon as possible.
A study describing the microneedle technology is published in the journal Nature Medicine.
