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Vaccine boosters are fast becoming the ultimate symbol of pandemic inequality. While much of the world struggles with procuring doses of the coronavirus vaccines, leaving health workers and other vulnerable people at risk, some wealthy nations are considering boosting the immunity of fully vaccinated people further with another shot.

But they will face opposition. The World Health Organization on Wednesday called for a global moratorium on booster shots until at least September, pointing to the urgent need for doses in poorer nations. “We cannot and should not accept countries that have already used most of the global supply of vaccines using even more of it while the world’s most vulnerable people remain unprotected,” WHO Director General Tedros Adhanom Ghebreyesus said at a media briefing.

The WHO had previously pushed for a target to get 10 percent of each country vaccinated by the end of September. In some countries, that target has been easily surpassed. By July 23, both North America and Europe had administered at least one vaccine dose to nearly half of all residents. But others lag far behind: Just over 2 percent of Africa’s population had been vaccinated by that time, according to figures compiled by The Washington Post.

Some experts fear that a rush for booster shots in wealthy nations could further upend an already unfair distribution of doses. Despite their recent donations of doses to nations with less vaccine access, the message to foreign health workers would be bleak. “You see the United States vaccinating its very healthy young people and planning on giving boosters to the elderly, you just have to shake your head and say, ‘Oh well, it’s nice you’re giving me a few doses,’” Lawrence Gostin, a professor of global health law at Georgetown University Law, told The Post this week. “It’s just exasperating.”

But with the rise of new variants, the push for additional shots is building in well-vaccinated countries. Booster shot campaigns are already underway in Israel and Russia, and are likely to start soon in parts of Europe: Germany, France and Britain have all announced plans for booster shots for certain segments of the population, The Post reported on Wednesday.

The United States has yet to recommend booster shots, but that may not be far off. “Those who are transplant patients, cancer chemotherapy, autoimmune diseases, that are on immunosuppressant regimens, those are the kind of individuals that if there’s going to be a third booster, which might likely happen, would be first among the vulnerable,” Anthony S. Fauci, the nation’s top infectious-disease expert, said during a CNN interview in late July.

Debate about booster shots has circulated since the early days of the pandemic, but concerns about fast-spreading variants like delta leading to “breakthrough” cases in vaccinated people have brought the issue to an inflection point. Although these cases are rare, they have coincided with a rise in cases among the unvaccinated and led to new guidance on masking and other restrictions.

Most Western leaders acknowledge the disparity of vaccine supply, but they remain focused on their own populations. It makes sense: These are the people who voted them into office and — possibly within a relatively short time — could vote them out again. Plus, with concerns about vaccinated people also spreading the virus, personally seeking a third shot to protect vulnerable family members or children may not necessarily seem selfish.

But for the drug companies that developed the vaccines, money may be a powerful motivator. In July, there was an unusual public spat between Pfizer (along with its German partner BioNTech) and the Department of Health and Human Services, with the U.S. agency resisting the drug company’s argument that additional doses may be needed. At the time, experts expressed concerns that drug manufacturers could play a biased role in the debate about the data for booster shots.

One report by Bloomberg Intelligence in May found that booster shots could represent an $11 billion to $37 billion market each year globally. Booster shots for wealthy nations are likely to be more profitable than initial shots in a poorer nations: For its first 1.3 billion doses, the global vaccine-sharing initiative Covax has said it paid an average of $5.20 per dose. Pfizer’s initial cost in the United States was $19.50 a shot — and that price is expected to increase.

Global experts are united in calling for equitable distribution of vaccines. They warn that leaders risk tackling short-term problems in place of long-term disasters. Scientists have warned again and again that allowing the virus to circulate unmitigated in poorer nations could allow potent variants to develop, not only threatening these nations but much of the already-vaccinated world.

Delta, the variant most widely discussed right now, was first identified in India, a nation where slow rates of vaccination had left a population ripe for infection. Another variant raising alarms, lambda, was first detected in Peru in August 2020 and quickly spread through much of Latin America. Vaccines still work well against these variants, but will they work against the next, or the one after that? Scientists simply can’t say for sure.

The impact on health workers and other vulnerable people in the developing world could be severe. It is also preventable. In the United States alone, vast numbers of doses are simply wasted when they could have been used. Stat News recently estimated that some U.S. states already had millions of excess doses, many of which were likely to expire before they could be used. Robert Ator, the head of the vaccine distribution drive in Arkansas said the state had so many doses, things were “starting to get a bit silly.” Ator told the health-news-focused website that his state was “drowning in this stuff.”

Vaccine donations can make a difference. The United States has sent more than 110 million doses to 65 countries, President Biden announced Tuesday. But while experts have cautiously praised these gestures, they’ve made clear that they do not go far enough. Beyond such donations, experts say, nations could move toward more powerful structural changes — for example, by sharing the technology behind mRNA vaccines. Though there is fear, however, that potential variants could limit future generosity.

“We have a supply for every single American,” Biden emphasized on Tuesday. Indeed, the United States has more than enough. According to tracking from the Global Health Innovation Center at Duke University, the United States has procured over 1.6 billion doses so far, which works out to about 5.21 doses per inhabitant. Vaccine boosters, along with wasted doses, put that amount at risk.

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