Pfizer Inc PFE.N has launched a pilot delivery program for its experimental COVID-19 vaccine in four U.S. states, as the U.S. drugmaker seeks to address distribution challenges facing its ultra-cold storage requirements, writes Reuters.

Pfizer’s vaccine, which was shown to be more than 90% effective in preventing COVID-19 based on initial data, must be shipped and stored at -70 degrees Celsius (minus 94°F), significantly below the standard for vaccines of 2-8 degrees Celsius (36-46°F).

“We are hopeful that results from this vaccine delivery pilot will serve as the model for other U.S. states and international governments, as they prepare to implement effective COVID-19 vaccine programs”, - Pfizer said in a statement.