The World Health Organization (WHO) has extended its call for member nations to hold-off on distributing COVID booster shots to their general populations until at least the end of the year due to widespread global vaccine assess inequality.

"A month ago, I called for a global moratorium on booster doses at least until the end of September, to prioritise vaccinating the most at-risk people around the world who are yet to receive their first dose," WHO Director-General Dr. Tedros Adhanom Ghebreyesus said in a media briefing Wednesday. "There has been little change in the global situation since then, so today I am calling for an extension of the moratorium until at least the end of the year, to enable every country to vaccinate at least 40% of its population."

The WHO estimates that roughly 5.5 billion vaccine doses have been administrer globally, but only 20% of that total have been distributed to lower-income nations. Moreover, almost 90% of high-income countries have vaccinated at least 10% of their population, and another 70% of rich nations have inoculated at least 40% of their citizens. The United States, for example, has administered nearly 379 million COVID vaccine doses and has effectively fully vaccinated over 53% of its entire population, according to data compiled by the Centers for Disease Control and Prevention.

"Not a single low-income country has reached either target. That's not their fault," Tedros said. "Manufacturers have prioritised or been legally obligated to fulfill bilateral deals with rich countries willing to pay top dollar, low-income countries have been deprived of the tools to protect their people."

The WHO has called for the equitable distribution of COVID vaccines since the start of the vaccine roll out, urging nations to prioritize doses for the world's vulnerable and frontline health care workers before mass inoculations of general populations. In addition to vaccines being life-saving tools, equitable distribution will also help mitigate the risk of new mutant variants that have the potential to be resistant to available vaccines, leading to risk of a new pandemic.

"High-income countries have promised to donate more than 1 billion doses, but less than 15% of those doses have been materialized," Tedros continued, adding that manufacturers have promised to prioritize doses for the WHO's COVAX initiative, but have failed to supply the shots in a timely manner.

"I will not stay silent when the companies and countries that control the global supply of vaccines think the world's poor should be satisfied with leftovers," Tedros said. "We don't want any more promises, we just want the vaccines."

The U.S. plans to start distributing booster doses to the general population on September 20, with the Pfizer (PFE  )-BioNTech (BNTX  ) vaccine expected to be the first approved by federal health regulators, according to top U.S. infectious disease expert Dr. Anthony Fauci. It is unclear whether or not the WHO's recommended booster shot moratorium will impact the White House's plans.