The virus has now infected more than 99 million people across the globe and has killed more than 2.1 million. The US remains the hardiest hit country, followed by India and Brazil. 

Two million doses of Covishield vaccine manufactured in India were flown to Brazil and another two million doses to Morocco on Friday. India is one of the world's biggest drugmakers, and an increasing number of countries have already approached it for procuring coronavirus vaccines.

US company Pfizer said it had fully enrolled its COVID-19 vaccine trial in kids ages 12 to 15, a key step before the vaccine could be used in that age group.

The WHO said that Covax has signed an agreement with Pfizer-BioNTech for up to 40 million doses of its COVID-19 vaccine. Covax -- the globally-pooled coronavirus vaccine procurement and equitable distribution effort, aimed at ensuring that lower-income countries get hold of doses too -- is hoping to ship its first deliveries in February.

Covax is co-led by the World Health Organization and Gavi, the Vaccine Alliance. The Pfizer-BioNTech vaccine is the only one so far to have received emergency use approval from the WHO.

Nearly 150 million doses of the AstraZeneca-Oxford vaccine were ready to ship through Covax -- pending emergency use approval from the WHO, which is on course to happen in mid-February.