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Microneedle patches: a new vaccine delivery approach

A new vaccine-delivery patch based on hundreds of microscopic needles that dissolve into the skin could allow persons without medical training to painlessly administer vaccines – while providing improved immunization against diseases such as influenza.

Patches containing micron-scale needles that carry vaccine with them as they dissolve into the skin could simplify immunization programs by eliminating the use of hypodermic needles – and their "sharps" disposal and re-use concerns. Applied easily to the skin, the microneedle patches could allow self-administration of vaccine during pandemics and simplify large-scale immunization programs in developing nations.

Details of the dissolving microneedle patches and immunization benefits observed in experimental mice were reported July 18th in the advance online publication of the journal Nature Medicine. Conducted by researchers from Emory University and the Georgia Institute of Technology, the study is believed to be the first to evaluate the immunization benefits of dissolving microneedles. The research was supported by the National Institutes of Health (NIH).

Just 650 microns in length and assembled into an array of 100 needles for the mouse study, the dissolving microneedles penetrate the outer layers of skin. Beyond their other advantages, the dissolving microneedles appear to provide improved immunity to influenza when compared to vaccination with hypodermic needles. 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.

Another advantage of these microneedles is that the vaccine is present as a dry formulation, which will enhance its stability during distribution and storage," said Ioanna Skountzou, an Emory University assistant professor. Pressed into the skin, the microneedles quickly dissolve in bodily fluids, leaving only the water-soluble backing. The backing can be discarded because it no longer contains any sharps.

The microneedle arrays were made from a polymer material, poly-vinyl pyrrolidone, that has been shown to be safe for use in the body. Freeze-dried vaccine was mixed with the vinyl-pyrrolidone monomer before being placed into microneedle molds and polymerized at room temperature using ultraviolet light.

In many parts of the world, poor medical infrastructure leads to the re-use of hypodermic needles, contributing to the spread of diseases such as HIV and hepatitis B. Dissolving microneedle patches would eliminate re-use while allowing vaccination to be done by personnel with minimal training.