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 ending global transmission would put everyone, including people in high-income countries, in a more dangerous position.
"If countries like Germany, like the US, like the UK choose to roll out booster shots before we have ensured that all communities worldwide have access to the first two doses of the vaccine, we're not really solving the problem ... It's a little bit like putting a Band-Aid over a gaping hole," said Taylor, who is leading research looking at global vaccine distribution at Duke.
"Just as we saw in South Asia, when there was uncontrolled transmission and the Delta variant really took off, there isn't anything to prevent that happening right now on the continent of Africa. And so, it's very likely that we could end up in a situation where we have even more dangerous, more transmissible, more infectious variants coming out of the spread that we are currently seeing in Africa."
Of the four major regions producing vaccines at a massive scale -- the US, EU, India and China -- the EU has exported the least, and that is even after India cut off exports following its deadly Delta-driven wave, Taylor said.
While the EU has made big pledges, it has been difficult to track its follow-through on donations. Even the European Commission's vice president has said the bloc is coming up woefully short on the 200 million doses it promised to deliver by the end of the year.
"Yes, but when?" Josep Borrell said to students in a university class in Spain, when discussing the EU's vaccine pledge, according to Politico Europe. "The problem isn't just the commitment but the effectiveness."
A commission spokesperson told CNN that as of August 2, the EU had donated 7.1 million doses to partner countries, including 1.59 million through COVAX, the WHO-led vaccine sharing program. "We are confident that member states will do their utmost to reach the 200 million doses pledge," the spokesperson added, shifting the onus of fulfilling that promise onto each of the 27 countries in the bloc.
Last week, UK Foreign Secretary Dominic Raab announced that the country would begin to deliver 9 million vaccines around the world -- the first of 100 million that Prime Minister Boris Johnson promised to share at last month's G7 summit in Cornwall, England.
Though the US has yet to announce a booster vaccination program, White House press secretary Jen Psaki appeared to reject WHO's call, telling reporters on Wednesday: "We definitely feel that it's a false choice and we can do both." President Joe Biden's administration last week celebrated shipping more than 110 million doses of coronavirus vaccines abroad -- most of which were shared through COVAX -- more than any other country.
Still, it's a drop in the bucket compared to the 11 billion doses that WHO says is needed to end the pandemic. So far, COVAX has shipped 188.1 million doses to 138 countries, according to data from the UN children's agency UNICEF.
WHO and other public health agencies argue that no one is safe until everyone is safe because the longer the coronavirus circulates unchecked, the greater the chance becomes of new variants emerging -- potentially one that is resistant to vaccines -- and prolonging the threat to the world. In spite of this, the West has continued to focus its attention on the "vaccine race" and frame the finish line of the pandemic as a domestic issue, rather than an international one.