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Microneedles Found Effective as Syringe for Measles Vaccine

Microneedle patches and conventional hypodermic needles (Gary Meek, Georgia Tech)

Microneedle patches and conventional hypodermic needles (Gary Meek, Georgia Tech)

Biomedical engineers at Georgia Institute of Technology and Centers for Disease Control and Prevention (CDC), both in Atlanta, found microneedle patches could deliver a vaccine for measles to lab animals as effectively as a conventional hypodermic needle. The team led by Georgia Tech’s Mark Prausnitz published its findings online in a recent issue of the journal Vaccine (paid subscription required).

The study involved not only a test of the microneedle delivery method, but also a process to devise a dry form of the measles vaccine — still requiring a live, although weakened virus — that could be stored temporarily on the microneedles and still produce an immune response. Measles vaccines given with hypodermic needles, the delivery method most used today, need to be kept refrigerated and reconstituted with sterile water before use.

These storage and preparation requirements can create logistical barriers for large-scale immunization programs, particularly in developing regions. In addition, trained and licensed medical staff are normally required to work with syringes, and used needles often must be tracked and discarded to prevent unauthorized reuse or misuse. Microneedles, while not reusable, would still need to be disposed as medical waste.

The microneedles used in the study are made of stainless steel, 750 microns (1 micron equals 1 millionth of a meter) in length, and arrayed on patch worn on directly on the skin. The Georgia Tech/CDC team, however, first had to develop a version of the conventional Edmonston-Zagreb measles vaccine that would work with microneedles. Because the vaccine contains a live virus in weakened form, say the researchers, made the task even more of a challenge.

The team tested adding a stabilizer that would not impair the effectiveness of the vaccine nor harm the people being immunized. The researchers found trehalose, a naturally-occuring sugar used as a food additive and stabilizer, resulted in minimal loss of viral concentration after 30 days in storage. They then dipped the microneedle patches in a liquid form of vaccine with trehalose and allowed the patches to dry.

Prausnitz’s team applied the vaccine-tipped microneedle patches to groups of lab rats in quantities ranging from the equivalent of 20 to 100 percent of human doses, and injected comparable numbers of rats with the conventional vaccine in the same doses. The results showed vaccination with the microneedles produces an immune response statistically indistinguishable from that produced by vaccination with the hypodermic needles.

While the findings point to the efficacy of microneedles for vaccinations, the process still needs refinements before it is ready for real-world use. The researchers are improving the stability of the dry vaccine with the goal of eliminating the need for any refrigeration, and are investigating polymer-based microneedles that would fully dissolve in the skin, removing the need to dispose of potentially infectious waste.

Prausnitz, with a colleague from Emory University, started Clearside BioMedical Inc., a company developing microneedle drug delivery systems to treat eye diseases that now require injections into the eye. Earlier this month, Clearside BioMedical successfully tested its system in clinical safety trials with human subjects.

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