“[Polio] still lurks in developing countries because vaccine storage and transport requires refrigeration. Now, scientists find freeze-drying a polio vaccine keeps it stable for as long as four weeks even in hot temperatures. The stability could enable vaccine distribution that could lead to the end of the disease.”

http://blogs.discovermagazine.com/d-brief/2018/11/27/freeze-dried-polio-vaccine-accelerates-polio-eradication-endgame/#.XL6G2ZNKjUY