The system, developed by researchers in Germany, features an extremely flexible hydrogel that stay intact until exposed to a particular substance. The vaccine is contained within an enclosure made of the hydrogel, and is released when the user takes a pill containing a compound that eventually makes its way to the capsule (in tests, the trigger compound was fluorescein). The delivery system has been successful in studies in mice.

Besides reducing the discomfort of shots, the pill-release method could provide relief for families who find it difficult to travel to medical clinics.