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The World Health Organization called Wednesday for a temporary moratorium on the use of Covid-19 vaccine booster shots by wealthy countries, saying the global priority should be on increasing supplies of first doses to countries that are still struggling to protect health workers and older adults.

Director-General Tedros Adhanom Ghebreyesus said that countries should hold off on starting to give booster doses until at least the end of September — though it was quickly clear that the global health agency might extend the call if vaccine doses available to lower-income countries do not increase to adequate levels.


Tedros said the aim of the moratorium would be to get enough vaccine supply into COVAX, the WHO-led international distribution system, to vaccinate 10% of the populations of all countries. That 10% includes people at the highest risk from Covid-19 infection.

“I understand the concern of all governments to protect their people from the Delta variant. But we cannot and we should not accept countries that have already used most of the global supply of vaccine using even more of it while the world’s most vulnerable people remain unprotected,” Tedros said during a news conference broadcast from the WHO’s Geneva headquarters.

Of the more than 4 billion vaccine doses that have been administered globally to date, more than 80% have gone to high-income countries that account for less than half of the world’s population, Tedros said. High-income countries have, on average, administered almost 100 doses for every 100 people in their populations; in low-income countries, 1.5 doses for every 100 people have been administered “due to lack of supply,” he said.


“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.

A small number of countries have started to give booster doses to their populations and a larger number of countries are contemplating it, said Kate O’Brien, WHO’s director of immunizations, vaccines and biologics. The United States is one of the countries grappling with the issue of booster shots.

Currently it is not clear that booster doses are needed, O’Brien said, noting that to move too quickly to adopt boosters would come at a high cost.

“This is a really big discussion about administering third doses to people who’ve already been vaccinated. And it’s incredibly important that we’re clear about what the data are, that the data are strong in supporting — or not supporting — whether or not those doses need to be administered,” she said. “If we’re not really grounded in that clarity, we’re going to be in a place where we have forever uncertainty about what actually should be done.”

The proposed moratorium is for broad use of booster shots. WHO officials said it is not meant to preclude giving additional doses to select populations who do not get protection from the standard regimen of vaccine.

Research shows that some people who are immunocompromised — for instance, people who have had organ transplants and are on immune-suppression drugs — get little or no protection from the vaccines as they are currently given. It’s been proposed that those people may need a regimen of three shots of vaccine, instead of the two-dose scheduled used for most people with most of the vaccines. (The Johnson & Johnson vaccine is used in a one-dose regimen.)

“There is increasing evidence that there are some populations … who don’t respond to the vaccine as well as the general population does,” said O’Brien. “We don’t want that to be confused with the policy …. of whether booster doses should be given.”

In May, the WHO called for affluent countries and vaccine manufacturers to increase efforts to supply vaccine to low-income countries, setting the target of getting 10% of people in all countries vaccinated by the end of September. At the current pace of distribution, that goal will not be achieved, Tedros said.

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