The World Health Organization has criticised the "greed" of rich countries considering COVID-19 booster vaccinations while the most vulnerable in other nations were left exposed to the virus.
Striking an increasingly exasperated tone, the WHO said the world would look back on itself with shame if it knowingly chose to leave the world's weakest at the mercy of the pandemic.
The UN's health agency also scolded vaccine manufacturers prioritising deals for booster third doses rather than first and second shots for the completely unvaccinated healthcare workers and elderly people in poorer nations.
WHO chief Tedros Adhanom Ghebreyesus told a press conference that the question he was most often asked was when the pandemic would end.
"We can end it very soon, because we have the tools now," he said - but for the lack of decisive global leadership.
Mr Ghebreyesus said vaccine nationalism was "prolonging the agony" and there was only "one word that can explain this... it's greed".
Rolling out booster doses while the virus rips through other parts of the world was counter-productive, he argued.
Mr Ghebreyesus insisted: "It doesn't even make any sense. It makes no sense."
A woman poses behind a cutout after receiving a Covishield vaccine in India. Source: AP
'Look back in shame'
WHO chief scientist Soumya Swaminathan said four countries had announced a booster program and a handful of others were known to be considering the move.
She stressed that there was currently "no scientific evidence to suggest that boosters are definitely needed".
Mr Ghebreyesus took aim at vaccine manufacturers.
He was referring to the program that is seeking to provide equitable access to doses for the most vulnerable.
WHO emergencies director Michael Ryan said that in a crisis, the most beneficial and lifesaving choices had to be made first.
"We will look back in anger and we will look back in shame if we don't now move to use the increasing production capacity that's coming on line... to protect the most vulnerable," he said.
Delta variant 'driving catastrophic waves'
Mr Ghebreyesus announced that two more sites making AstraZeneca's vaccine under licence in Australia and Japan had now been given the WHO's emergency use listing green light, adding to the plants in Europe, India and South Korea already churning out AZ doses.
"If AstraZeneca does it, why can't others?" asked Mr Ghebreyesus, urging manufacturers to let other plants produce their jabs.
AstraZeneca jabs have made up the vast majority of doses supplied so far through Covax.
More than 3.35 billion doses of COVID-19 vaccines have been injected in at least 216 territories around the world, according to an AFP count.
In high-income countries, as classified by the World Bank, 86 doses have been injected per 100 inhabitants.
That figure stands at just one dose per 100 in the 29 lowest-income countries.
Mr Ghebreyesus noted that last week marked the fourth consecutive week of increasing COVID-19 cases globally, and after 10 weeks of decline, deaths are increasing again.
"The Delta variant is ripping around the world at a scorching pace," he said, "driving catastrophic waves of cases" in countries with low vaccination rates.
Delta has been found in more than 104 countries and is soon expected to become the dominant COVID-19 variant circulating worldwide, said Mr Ghebreyesus.
