As some countries struggle to get first doses of COVID-19 vaccines to their most vulnerable, other nations are already moving ahead with plans to offer supplementary "booster" shots.

On Wednesday, the World Health Organization called for a moratorium on COVID-19 vaccine boosters through the end of September or later, citing global inequalities in the vaccine rollout.

The statement came hours after a San Francisco hospital began offering "supplemental doses" of the Pfizer or Moderna vaccines to Johnson & Johnson recipients – following the lead of countries like Israel, which is already offering Pfizer boosters to elderly people, and European countries, planning to start boosters next month.

About 29 percent of the world's population has received at least one dose of a COVID-19 vaccine, but that number is close to 1 percent in low-income countries, according to Our World in Data.

"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," director general Tedros Adhanom Ghebreyesus said on Wednesday.

Israel, France, and Germany are starting to roll out boosters already

Israel has begun offering booster shots of the Pfizer-BioNTech vaccine to people over 60. President Isaac Herzog kicked off the campaign by getting his third shot of the vaccine on Friday, Reuters reported.

Germany and France are also on track to begin administering third doses to those who were vaccinated early in the rollout. In both countries, elderly folks and people with compromised immune systems will be able to book booster appointments in September.

The UK is prepared to start in September as well, pending approval from national health experts, according to the Washington Post.

The US CDC has yet to come out with guidance on third shots, but the White House said it is prepared to provide boosters if needed, Reuters reported.

Following the WHO's statement Wednesday, press secretary Jen Psaki said Washington can both provide booster shots if they are approved for use and donate excess supplies to other countries.

However, if the 11 countries that are either rolling out boosters or considering it this year were to give the shots to everyone over 50 years old, they would use up roughly 440 million doses of the global supply, according to an analysis by the WHO.

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

This article was originally published by Business Insider.

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