Microneedle Vaccination Technique Protects Rabbits Against Inhalation Anthrax Using Smaller Dosage

The anthrax attacks of September 2001, which killed 5 people and sickened many more, spurred an unprecedented level of support for the development of new treatment and prevention methods. Antibiotics have shown to be 100% effective at treating the cutaneous form of anthrax, however inhalation anthrax has a fatality rate of 75% or higher even with antibiotic treatment. The vaccine currently available is administered intramuscularly (i.m.), but recent studies suggest that intradermal (i.d.) delivery (in the skin) can increase the immune response while utilizing smaller doses, which is much more difficult to do with a conventional needle.

In the study researchers compared the efficacy of immunizing rabbits with the current anthrax vaccine intradermally using a microneedle and intramuscularly using a conventional needle. Results showed that intradermal delivery required less dosage to induce similar antibody levels as those seen following intramuscular injection. Rabbits that were administered the vaccine using the microneedle-based technique showed protection against inhalation anthrax at 100%, while those vaccinated using conventional methods were protected at 71%. Groups receiving lower dosages of the vaccine displayed partial protection regardless of vaccination technique.

"Our results suggest that i.d. delivery induces a level of protection against inhalation anthrax in a rabbit model that is comparable to that achieved via i.m. injection using conventional needle and syringe technology," say the researchers. "The use of minimally invasive, easy-to-use delivery devices such as the microneedle-based system described herein could potentially reduce the burden on highly skilled medical practitioners for biodefense vaccination.

(J.A. Mikszta, J.P. Dekker III, N.G. Harvey, C.H. Dean, J.M. Brittingham, J. Huang, V.J. Sullivan, B. Dyas, C.J. Roy, R.G. Ulrich. 2006. Microneedle-based intradermal delivery of the anthrax recombinant protective antigen vaccine. Infection and Immunity, 74. 12: 6806-6810.)