"A team of researchers, led by a University of Minnesota associate professor, have developed a polymer "wafer" that, when placed under the tongue, can effectively deliver and preserve protein-based vaccines for diseases. The research could open the door for vaccines that can be more easily produced and distributed to communities around the world. The study is published in the Journal of Controlled Release.

The membrane under the tongue, called the sublingual site, has proven to be very effective at absorbing drugs. Several drugs are delivered this way, such as nitroglycerin tablets to treat chest pain that precedes heart attacks. But large molecules, such as the proteins and nucleic acids that make up many vaccines, have historically been too big to enter the body sublingually and have to be injected with needles. These large molecules are also very fragile and must be preserved, which can be a roadblock for vaccine distribution—for example, Pfizer's COVID-19 vaccine, which is made up of nucleic acids and requires ultra-cold storage."

https://medicalxpress.com/news/2021-05-polymer-wafers-tongue-vaccines-future.html