Despite the repeated warnings of health leaders, our failure to put vaccines into the arms of people in the developing world is now coming back to haunt us. We were forewarned – and yet here we are. In the absence of mass vaccination, Covid is not only spreading uninhibited among unprotected people but is mutating, with new variants emerging out of the poorest countries and now threatening to unleash themselves on even fully vaccinated people in the richest countries of the world. On Thursday, the UK’s Department of Health, which has placed a travel ban on southern Africa, warned that the B.1.1.529 “Omicron” variant was the most “complex” and “worrying” seen so far. And yet with 9.1bn vaccines already manufactured and 12bn expected by the year’s end – enough to vaccinate the whole world – this was the “arms race” that we could have won. No country should be facing yet another winter with the uncertainty of a new wave of Covid hanging over us. On Monday, the World Health Assembly, the decision-making body of the World Health Organization, will meet in a special session. They will hear that vaccination rates in the six countries now subject to UK travel bans are still dangerously below the 40% target that was set for December. In Zimbabwe, only 25% have had a first vaccine and just 19% of the population are fully vaccinated. In Lesotho and Eswatini, which have had the Johnson and Johnson single-shot vaccines, just 27% and 22% respectively have been vaccinated. In Namibia the figure is even lower: 14% vaccinated with only 12% fully vaccinated. While South Africa has achieved 27% vaccination rates, its rural areas are often in single figures, and the whole of the continent is justifiably angry because their own efforts to vaccinate have been impeded for months by the neo-colonialism of the European Union. Even as the gap between the vaccines haves of Europe and the vaccine have-nots of Africa mushroomed, the EU insisted on commandeering millions of South African-produced Johnson & Johnson one-shot vaccines and sending them out of Africa into Europe. In June, Boris Johnson promised he and the G7 countries would use their surplus vaccines to immunise the whole world. In September, at a summit chaired by President Biden, a December target of 40% vaccination was set for the 92 poorest countries. Two and a half months on, there is little chance of this target being met in at least 82 of them. By Thursday the US, which to its credit has been responsible for half the vaccines donated, had still delivered only 25% of the vaccines that it promised. The arithmetic of failure in the rest of the world is even more embarrassing. According to Airfinity, the European Union has delivered only 19%, the UK just 11% and Canada just 5%. China and New Zealand have delivered over half of what was promised, but their pledges amounted to just 100m and 1.6m respectively. Australia has given just 18% of what it offered and Switzerland just 12%. The result is that even now only 3% of people in low-income countries are fully vaccinated, while the figure exceeds 60% in both high-income countries and upper-middle-income countries. Every day, for every vaccine delivered as first vaccines in the poorest countries, six times as many doses are being administered as third and booster vaccines in the richest parts of the world. This vaccine inequality is the main reason why the WHO is predicting 200 million more cases on top of the 260 million so far. And after 5 million deaths to Covid, another 5 million are thought to be possible in the next year and more. What’s most galling is that this policy failure is not because we are short of vaccines or manufacturing contracts to secure them. The problem is not now in production (2 billion doses of vaccine are being manufactured every month), but in the unfairness of distribution. The stranglehold exercised by the G20 richest countries is such that they have monopolised 89% of vaccines, and even now, 71% of future deliveries are scheduled for them. As a result, the global vaccine distribution agency, Covax, has been able to secure only two-thirds of the 2bn vaccines promised to poorer countries. The good news is that our medical genius has ensured that the new Omicron variant has been identified quickly; is being sequenced at speed; and, if it proves not only more transmissible but immune to current vaccines, a new vaccine could potentially soon emerge. But given the contrast between the success of our scientists and the failure of our global leaders, only a herculean effort starting this week can allay fears that new mutations among unvaccinated people in the least-protected places will take Covid into a third year – with even fifth, sixth and seventh waves. We can act quickly. As of today, 500m unused vaccines are available across the G7. By December, the figure will rise to 600m, and by February, it will be 850m vaccines, which can be sent to the countries in greatest need. At the last count, the US has 162m vaccine doses it could immediately deliver to the rest of the world, a figure that grows to 250m next month; Europe currently has even more: 250m, which by February could exceed 350m. The UK has 33m vaccines – expected to rise to 46m over the next three months. The alternative is too awful to contemplate; vaccines are being destroyed while lives are being lost through lack of them. According to the data research agency Covax, around 100m of western countries’ vaccines will pass their use-by dates in December and could easily go to waste. Of course, there will be issues of absorption in Africa, but the bigger problem is that too many of the vaccines gifted to the poorest countries are within 12 weeks of their “use-by-dates”. These short lead times between donation and expiry show why a strengthened G20 and a month-to-month delivery timetable is now urgent; and why the expeditious transferring of delivery dates, from rich to poor countries – as has happened with Switzerland’s recent transfer to Covax – is the best way of speeding up the transfer of unused vaccines to where they are needed most. Nothing so dramatically illustrates the urgent need for what might be called a pandemic non-proliferation treaty . A new and binding international agreement that the World Health Assembly will consider next week must improve our surveillance and early warning systems, ensure the early transfer of medical supplies to countries in need, and finally agree sufficient funding of a worldwide effort to deliver what is clearly the most important global public good of all: cross-border control of infectious disease. Only when we reject vaccine nationalism and medical protectionism will we stop outbreaks becoming pandemics. Gordon Brown is the WHO ambassador for global health financing, and was UK prime minister from 2007 to 2010