When a COVID-19 vaccine is approved for use, one of the next major challenges will be logistical: How do you distribute billions of doses around the planet, including to remote corners of the world that lack reliable electricity, when the vaccine has to stay refrigerated to be effective?

UNICEF is building a global network of fridges and cold rooms—the cold chain—to make sure a vaccine stays effective as it’s transported to rural communities off the grid.

Read more: Fast company