GENEVA/LONDON (Reuters) – The COVAX vaccine-sharing program said on Tuesday it will deliver 237 million doses of AstraZeneca’s COVID-19 shot to 142 countries by the end of May as it steps up the global roll-out of its vaccine supplies.

The timeline for the delivery of doses, made by AstraZeneca and by India’s Serum Institute, will be split into separate two-month schedules, COVAX said in a statement, with the first in February-March and the second in April-May.

“These timelines are dependent on a variety of factors including national regulatory requirements, availability of supply, and fulfillment of other criteria such as validated national deployment and vaccination plans,” the statement said.

COVAX is the World Health Organization-backed program to provide vaccines for poor and middle-income countries. It began its roll-out last week with the first deliveries of shots to Ghana and Ivory Coast.

Hailing the campaign as an “unprecedented partnership,” WHO Director-General Tedros Adhanom Ghebreyesus said Angola, Cambodia, Democratic Republic of Congo and Nigeria could also expect deliveries of COVAX-supplied vaccines on Tuesday.

“This is an unprecedented partnership that will not only change the course of the pandemic but also change the way the world responds to future health emergencies,” Tedros told a joint media briefing with the U.N. Children’s Fund UNICEF, the GAVI vaccines alliance – which co-leads COVAX – and others.

Ghanaian President Nana Akufo-Addo told the same briefing that his West African country, which this week began its inoculation campaign with COVAX doses, aimed to vaccinate 20 million people by the end of 2021.

COVAX added in a statement that as well as the first round of allocations of the AstraZeneca vaccine, some 1.2 million doses of the Pfizer-BioNTech COVID shot were also anticipated for delivery in the first quarter of 2021.

(Reporting by Emma Farge and Stephanie Nebehay in Geneva and Kate Kelland in London; Editing by Mark Heinrich)