GENEVA: The World Health Organization on Tuesday urged the 20 leaders with the power to overturn the "disgraceful" global imbalance in access to Covid-19 vaccines to reverse the tide before October.

The WHO's Bruce Aylward said the world should be "disgusted" -- and asked whether the situation could have been any worse had there been an active effort to block the planet's poor from getting vaccinated.

The UN health agency has been increasingly infuriated by what it sees as the moral outrage of rich countries hogging vaccine supply while developing nations struggle to immunise their most vulnerable populations.

Aylward, the WHO's frontman on accessing the tools to fight the coronavirus pandemic, urged people to tell politicians and business tycoons that it was electorally and financially safe to increase vaccine coverage in poorer nations.

"There's probably 20 people in the world that are crucial to solving this equity problem," he told a WHO social media live interaction.

"They head the big companies that are in charge of this; they head the countries that are contracting most of the world's vaccines, and they head the countries that produce them.

"We need those 20 people to say, 'we're going to solve this problem by the end of September. We're going to make sure that 10 percent of every country... is vaccinated'."

Nearly 4.5 billion vaccine doses have been administered around the world, according to an AFP count.

In high-income countries, as categorised by the World Bank, 104 doses have been injected per 100 people.

In the 29 lowest-income nations, just two doses have been administered per 100 people.

"We should be collectively disgusted with ourselves," said Aylward.

"I can't help but think: if we had tried to withhold vaccines from parts of the world, could we have made it any worse than it is today?

"We need 20 people to lead the world's effort to change what is a disgraceful situation we're in."

The WHO wants every country to have vaccinated at least 10 percent of its population by the end of September; at least 40 percent by the end of this year, and 70 percent by the middle of 2022.