The United Nations children’s agency launched an initiative Tuesday to get airlines to give priority to delivering coronavirus vaccines, medicine and other critical supplies to respond to the global pandemic.

UNICEF said more than 15 airlines have signed agreements to support the priority delivery of pandemic-related materials.

“Delivery of these life-saving vaccines is a monumental and complex undertaking, considering the sheer volumes that need to be transported, the cold chain requirements, the number of expected deliveries and the diversity of routes,” said Etleva Kadilli, director of UNICEF’s supply division.

UNICEF said its Humanitarian Airfreight Initiative brings together airlines covering routes to over 100 countries, in support of the U.N.’s unprecedented COVAX program to buy and deliver coronavirus vaccines for hundreds of millions of the world’s poorest people.

Based on COVAX’s initial first round allocation plan, UNICEF said 145 countries will receive doses to immunize around 3% of their populations, on average, starting in the first half of 2021, “subject to all requirements being met and final allocation plans.”

In addition to prioritizing COVID-19-related shipments, UNICEF said the airlines will take measures including ensuring temperature control and security as well as adding freight capacity to routes when needed.

It identified airlines that signed the agreement so far as AirBridgeCargo, Air France/KLM, Astral Aviation, Brussels Airlines, Cargolux, Cathay Pacific, Emirates Skycargo, Ethiopian Airlines, Etihad Airways, IAG Cargo, Korean Air, Lufthansa Cargo, Qatar Airways, SAUDIA, Singapore Airlines and United Airlines.