GENEVA, Switzerland - The WHO said it was supporting the five remaining countries yet to start their COVID-19 immunization campaigns, as the planet clocked up administering three billion vaccine doses on Tuesday.

Vaccination has yet to get under way in Burundi, Eritrea, Haiti, North Korea and Tanzania -- the only countries among the World Health Organization's 194 member states yet to begin immunization programmes in the fight against the coronavirus pandemic.

"WHO continues to support these countries in decision-making on the introduction of COVID-19 vaccines," a spokeswoman told AFP.

WHO director-general Tedros Adhanom Ghebreyesus wanted every country to start vaccinating their health workers and those most vulnerable to COVID-19 disease within the first 100 days of 2021 -- a date that passed in April.

However, rich countries hogging the batches rolling off the production lines has left some countries waiting to administer their first doses.

"We are facing a two-track pandemic, fuelled by inequity," Tedros said Tuesday.

The Covax facility, aimed at ensuring poorer countries get access to vaccines, has so far delivered 89 million doses to 133 participating territories.

But supply lines have all but dried up this month, according to the WHO, which co-runs the scheme.

"The world is failing," Tedros warned.