London (CNN)The war against Covid-19 is changing, putting into stark relief the deepening divide between countries that have the weapons to fight the virus and those that don't.
As concerns mount over the highly contagious Delta variant, wealthy nations are tightening their grip on vaccine arsenals, while desperate people elsewhere in the world are dying due to a lack of shots.
Teetering on the edge of a dreaded new wave of coronavirus infections, the United States and Europe are deploying a barrage of monetary incentives and mandates to convince vaccine holdouts to get off the fence, and momentum is building to dole out booster shots for vulnerable groups.
Officials in the US and the European Union have one eye trained on the United Kingdom, where the government was slammed last month for dropping nearly all coronavirus restrictions in England. Critics described the move as a "dangerous and unethical experiment," just as the country was in the midst of a frightening Delta-fueled spike in infections. Now cases appear to be subsiding, raising questions about whether Britain's highly vaccinated population may be on the cusp of some sort of herd immunity, but epidemiologists say it's too early to tell.
Meanwhile, around the world, hundreds of millions of people are still waiting to receive their first dose of a coronavirus vaccine and the prospect of widespread immunity feels like a pipe dream.
Africa and Southeast Asia, where vaccine rates are low, are seeing some of their worst coronavirus outbreaks of the pandemic. Authorities are being confronted with a pressing and seemingly insurmountable problem: How to reduce deaths without doses, and among populations who can no longer afford to stay at home.
International agencies, humanitarian aid organizations, infectious-disease specialists and ethicists have all cautioned countries against seeking booster shots until more data becomes available about whether or not they're needed, calling instead for governments with a surplus to donate doses to poorer nations struggling with supply issues and rising outbreaks. But the Delta variant has changed that calculation for officials in the US and EU, who are furiously attempting to avert another winter wave of the virus and avoid the daunting task of reimposing lockdowns.
On Wednesday, World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus called for a moratorium on vaccine boosters until at least the end of September, with the goal of getting 10% of every country's population vaccinated by then.
"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 the world's most vulnerable people remain unprotected," Tedros said.
High-income countries have administered nearly 100 doses for every 100 people, according to WHO, while low-income countries have only been able to administer 1.5 shots for every 100 people, due to a lack of supplies.
"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, calling on leaders from the Group of 20, which includes the US and EU, to do more to improve access globally.
Germany and France have disregarded the appeal, saying they would press ahead with plans to administer boosters to the vulnerable while simultaneously fulfilling their philanthropic pledges, but it is unclear whether they, or any other country, have the capacity or the will to deliver on both.
Andrea Taylor, assistant director of programs at Duke University's Global Health Innovation Center, told CNN that prioritizing booster shots over