The COVAX vaccine-sharing program has so far shipped almost 50 million doses of COVID-19 vaccines to 121 countries and economies, but still faces severe supply constraints, said World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus in a media briefing on Monday.

A sum of $35 billion to $45 billion is further needed over the next year to ensure that most adults are immunized, according to Ghebreyesus.

He also appealed to the G7 countries, whose foreign ministers are meeting in London, to mobilize a substantial portion of these funds themselves and lead a global effort to accelerate vaccination around the world.