“The microneedles are small, so it just looks like something shiny on the surface of the patch,” says Prausnitz. He and his colleagues make the patches using a mold they built themselves, forming the microneedles from a solution that includes the vaccine, sugars and polymers. They let the solution dry overnight and pull out a sheet of microneedles in the morning…

Putting the vaccine in a patch eliminates the need for a medical professional and a refrigerator. “It would enable us to get the vaccine to a lot more people,” says Prausnitz.

The patch has another advantage. No needles to dispose of — so no risk of health workers getting stuck with a discarded needle. Once the patch is pulled from a person, the needles are gone and the patch can be tossed.