Gavi, the Vaccine Alliance said on Monday it had signed an advance purchase agreement with Moderna to secure 500 million doses of its COVID-19 vaccine for the global COVAX program.

"We are very pleased to sign this new agreement with Moderna, giving COVAX Facility participants access to yet another highly efficacious vaccine," said Dr. Seth Berkley, CEO of Gavi. 

The roll out of the purchase will start in the fourth quarter, with 34 million doses available this year, Gavi said on Monday.

The announcement came as Sweden also plans to donate 1 million doses of AstraZeneca's vaccine to COVAX.

(With input from Reuters)