WHO Director General Dr Tedros Adhanom Ghebreyesus said while hundreds of millions of people are still waiting for their first dose, some rich countries are moving towards booster doses.

"I understand the concern of all governments to protect their people from the Delta variant. But we cannot accept countries that have already used most of the global supply of vaccines using even more of it, while Europe and Africa's most vulnerable people remain unprotected," he added.

He went on to reiterate the call for "sprint to September" he issued in May where he sought cooperation to ensure that every country is able to vaccinate at least 10 percent of its population.

"We are now more than halfway to that target date, but we are not on track," the WHO chief said on Wednesday.

Dr. Ghebreyesus said the health ministers of G20 nations will meet one month from now ahead of the G20 summit in October. It is no understatement to say that the course of the Covid-19 pandemic depends on the leadership of the G20, added Dr. Ghebreyesus.

"I call on them to make concrete commitments to support WHO's global vaccination targets," he said. He also appealed to vaccine producers to prioritize COVAX - the WHO's vaccine alliance.

Dr. Ghebreyesus stated, "So far, more than 4 billion vaccine doses have been administered globally. More than 80 per cent have gone to high and upper-middle-income countries, even though they account for less than half of the world's population."

The WHO chief went on to add that low-income countries have only been able to administer 1.5 doses for every 100 people due to lack of supply of Covid-19 vaccines. Populations that cannot afford to stay at home need vaccinations urgently, he added.

Low-income countries, on the other hand, have only been able to administer 1.5 doses for every 100 people owing to the lack of supply.

Recalling the challenge he made in May of this year, the WHO chief said high-income countries had administered around 50 doses for every 100 people at the time. He adds that the number has doubled since and high-income countries have now administered almost 100 doses for every 100 people.

Dr Ghebreyesus also cited an email from Harriet Nayiga, a midwife from Uganda who is one of many health workers in Africa and other parts of the world still waiting for their turn to receive the lifesaving jab.

"We need an urgent reversal, from the majority of vaccines going to high-income countries, to the majority going to low-income countries," he said.

Dr Tedros Adhanom Ghebreyesus added, "We call on everyone with influence; Olympic athletes, investors, business leaders, faith leaders, and every individual in their own family and community to support our call for a moratorium on booster shots until at least the end of September."