Australia and the Philippines limited use of AstraZeneca's COVID-19 vaccine on Thursday, while the African Union dropped plans to buy the shot amid global shortages, dealing further blows to the company's hopes to deliver a vaccine for the world.

The vaccine - developed with Oxford University and considered a frontrunner in the global vaccine race - has been plagued by safety concerns and supply problems since Phase III trial results were published in December, with Indonesia the latest country forced to seek doses from other drugmakers.