COVID-19 vaccines developed by China are being shipped to countries across the world.

Produced by one of China's major vaccine makers, Sinovac Biotech, they must be kept below a specific temperature to remain active.

Before they're shipped out of a production plant in Beijing, the vaccines are loaded into temperature-controlled containers and sent to the airport by cold-chain trucks.

On Wednesday, a cargo flight from Swissair picked up vaccines at the Beijing Capital International Airport to deliver them to Brazil before Christmas. With international commercial flights hampered by the pandemic, airfreight is now a major mode of vaccine transport.

Beijing Aviation Ground Service Co. Ltd. (BGS) is the local logistic company responsible for handling the vaccines from the production plant until they are loaded onto an airplane. It is the second company in China certified by the International Air Transport Association (IATA) and the Center of Excellence for Independent Validators in Pharmaceutical Logistics (CEIV Pharma).

"This isn't a new task for us, but delivering vaccines in such a great quantity is something we haven't seen before," said Yan Xin, director of BGS's International Cargo Division. "We've set up a special team to handle the process and to ensure the vaccines are well protected and shipped out in the most efficient way."

Temperature sensors were put both inside and outside the container to record the temperature throughout transportation, and the team also checked to make sure the containers' battery was fully charged before it was loaded onto the airplane.

Aviation medicine cold-chain logistics has always been the focus of global airlines. However, opportunities and challenges co-exist in the huge market.

The freight business has become a "sanctuary" for airlines in extremely difficult times, with many operating at unprecedented profits in 2020. When quarantines and blockades disrupt flights, freight costs soar, helping operators keep the remaining passenger routes open and avoid bigger deficits. IATA forecasts that airfreight revenues will triple this year to 36 percent, thanks to a 30-percent rise in average freight prices.

China's major airlines are all enhancing their cold-chain transport capacity, preparing for an imminent need for vaccine transport. Airports are also making preparations. In mid-November, Shenzhen Airport was officially certified as an independent pharmaceutical logistic verification center by IATA, meaning that countless vaccines will be shipped and distributed through the region in the future.

Currently, only China's Beijing, Shanghai and Shenzhen have airports with this certification.