In an effort to simplify influenza vaccine administration and improve vaccine immunogenicity, Mark Prausnitz of the Georgia Institute of Technology in Atlanta and colleagues have developed polymer microneedle patches containing inactivated influenza virus. Results from a study in mice suggest that similar dissolving patches could be used for safer and simpler vaccination in humans and could help increase vaccine uptake rates (Nat. Med. 16, 915–920; 2010).

The research team designed polymer microneedle patches so that the devices would encapsulate the influenza virus without disrupting its antigenicity, would insert into the skin and would rapidly dissolve into safe products. Each patch encapsulates 3 μg of inactivated flu virus and consists of an array of needles that are just hundreds of micrometers in length.

The researchers administered a single, 6-μg dose of inactivated flu virus vaccine to 11 female mice using microneedle patches and to 11 female mice using intramuscular immunization. To intradermally administer the 6-μg dose to a mouse, the researchers applied two microneedle patches to the mouse's skin for 15 minutes and then removed the patches. A month later, the researchers exposed six mice from each group to a lethal dose of flu. All of the mice that had received the vaccine through either the patches or intramuscular injection lost less than 5% of their body weight and survived this challenge dose. A group of six mice that had not received vaccination lost more than 25% of their body weight within a week of the challenge.

Three months after immunization, the research team exposed mice to flu particles, allowing the animals to inhale the flu particles. Four days after this exposure, the mice that had received the microneedle vaccination had cleared about 1,000 times more viral particles from their lungs than had the mice that had received intramuscular vaccination. These results highlight the potential benefits of immunizations that target the skin, which is an active immune organ with ample antigen-presenting cells.

In their paper, Prausnitz and colleagues note that “the effectiveness of influenza vaccination is limited by the quality and breadth of the immune response and the time required for vaccine delivery.” Additionally, some people are afraid of the needles used to administer vaccines intramuscularly, and intramuscular injections create biohazardous waste, the authors note. The research team concludes that these microneedle patches provide an alternative tool for flu vaccine administration that is simpler and safer and results in higher immunogenicity.