The World Health Organization has granted an emergency authorization to the coronavirus vaccine made by AstraZeneca and Oxford University.

The move should allow the U.N. health agency's partners to ship millions of doses to countries as part of a U.N.-backed program to tame the pandemic. The WHO said it was authorizing the AstraZeneca vaccines made by the Serum Institute of India and South Korea’s AstraZeneca-SKBio.

It is the second vaccine green-lighted by WHO after the Pfizer-BioNTech vaccine was approved in December. The AstraZeneca vaccine has been licensed in over 50 nations but some African health experts worry it may be less effective against a virus variant first seen in South Africa.