There’s a grim inevitability to the fact that the latest concerning strain of the Covid-19 virus — known as B.1.1.529, and now nicknamed the Omicron variant 1 — should have been first identified in South Africa.

So far, SARS-CoV-2’s most devastating impacts have been in developed countries. The US, UK and European Union have accounted for about a third of deaths, compared to their roughly 10% share of the world’s population. However, it’s been in the BRICS grouping of fast-growing middle- income nations where an outsized share of new variants of concern have been isolated and analyzed for the first time. From the original strain in China, to the Delta lineage picked up in India, the Gamma variety isolated in Brazil and the Beta and latest Omicron strains from South Africa, only the UK-related Alpha variant has emerged outside these countries.

In part, that’s just a reflection of the fact that two out of five people in the planet live in one of the BRICS nations. It’s also no coincidence that new variants were first identified in countries with the sophisticated scientific infrastructure needed to spot them. The BRICS are some of the biggest players in the global market for generic drugs, and the likes of India and South Africa have performed a key role in debates over intellectual property waivers to increase access to medicines.

At this point, though, the crucial factor may be the fact that richer countries are now mostly so heavily vaccinated that the opportunities for the virus to cook up new mutations are increasingly limited. The nations with the largest populations of unvaccinated and susceptible citizens are those where the odds are greatest that SARS-CoV-2 will find a new way of breaking through the barriers we’ve placed in its path.

“Escaping from immunity is something that viruses do really well,” said Ian Mackay, an associate professor of virology at the University of Queensland. “If there are lots of populations that are still susceptible, we’re in the same kind of hamster wheel of this that we’ve been in before.”

It’s too early to know much about how the latest variant will affect people. One concerning aspect is the remarkably large number of mutations, particularly to aspects of the genome that affect the virus’s ability to transmit itself to others or fight back against the body’s immune responses. That raises the prospect that it could, as with Delta, spread more rapidly through non-immune populations, or even break through the protections of those who’ve already been infected or vaccinated.

At the same time, the sheer diversity of mutations means it will be hard to know for sure whether these changes will amplify or cancel each other out until we’ve been able to observe the latest variant’s progress in humans, said Mackay.

We don’t need the answer to those questions, however, to know the mistake the rich world is already making in treating Covid-19 as a pathogen that’s already been defeated by its own high rates of vaccine coverage. While the likes of China, Japan, France, Italy, South Korea and Canada can boast that three-quarters of their populations are fully immunized, 110 of the 200 countries and territories for which Bloomberg has data are shy of 50% (the US, at 59%, has one of the worst records in the developed world). Of that number, 64 haven’t even reached 25%, including South Africa itself. India, at 31%, and Russia at 37% aren’t doing much better. Of the 37 nations with less than 10% fully protected, 32 are in sub-Saharan Africa.

That yawning gap is being driven by the glacial pace at which pharmaceutical companies in the rich nations where drugs have been developed have been sharing their intellectual property with generics producers in emerging economies. While the US decision in May to waive IP rules around Covid-19 drugs was a major step toward addressing that problem, European opposition and a lack of compulsion from governments have failed to produce the change needed to increase supplies.

“The current vaccine equity gap between wealthier and low resource countries demonstrates a disregard for the lives of the world’s poorest and most vulnerable,” the heads of the World Health Organization and International Organization for Migration and United Nations High Commission for Refugees wrote in an open letter to Group of 20 leaders last month. “Vaccine inequity is costing lives every day, and continues to place everyone at risk.”

As natural and vaccine-derived immunity rises, viral evolution will have to get more and more ingenious to evade our defenses. So far, scarcely more than half of the world’s population has had a dose of a Covid vaccine. That means there’s still more than 3.4 billion people out there whose bodies the virus can treat as laboratories in which to develop new mutations. Until we reduce that number further, the odds aren’t as strongly in our favor as we’d like to think.