The Covax vaccine facility has delivered nearly 38.4 million doses of Covid-19 vaccines to 102 countries and economies across six continents, six weeks after it began to roll out supplies, according to a statement on Thursday.
The programme offers a lifeline to low-income countries in particular, allowing them in the first instance to inoculate health workers and others at high risk, even if their governments have not managed to secure vaccines from the manufacturers.
But there have been some delays, the GAVI vaccine alliance and World Health Organisation said in a statement.
Reduced availability of delayed some deliveries in March and April, and much of the output of the Serum Institute of India, which makes the AstraZeneca vaccine, is being kept in India, where daily infections surpassed 100 000 for the first time on Monday.
The 102 countries reached so far include 61 benefiting from a mechanism essentially financed by donors.
WHO Director-General Tedros Adhanom Ghebreyesus on Monday called it a "travesty" that some countries still did not have enough vaccines to begin inoculating health workers and the most vulnerable.
GAVI said last month that it planned to deliver 237 million doses of the AstraZeneca vaccine - which has been produced at cost for a few dollars a dose, and does not require the advanced refrigeration of some other coronavirus vaccines - to 142 countries by the end of May.
Covax still expects to deliver at least 2 billion doses this year 2021, and to diversify the offering beyond the AstraZeneca/Oxford and Pfizer/BioNTech shots it is currently supplying.
Meanwhile, Covax has backed the AstraZeneca vaccine, amid reports that it can lead to blood clots.
AstraZeneca's Covid-19 vaccine accounts for almost the entire first wave of doses being distributed via the facility, which ensures the 92 poorest participating economies can access jabs for free.