The poorest and most crisis-hit countries could remain "stuck" in pandemic crisis mode until at least 2023 unless more is done to provide aid and vaccines, the British head of the UN humanitarian programme has warned.
That means the devastating knock-on effects of Covid-19 - including the risk of famine in a number of countries - will also be prolonged and intensified, said Mark Lowcock, the UN's humanitarian chief.
Speaking to The Sunday Telegraph, he said: "Suppose the better-off world gradually comes out of this challenge... how do we make sure that the very poorest countries, where humanitarian agencies work, don't just get stuck? That's going to be one of the big challenges for 2021 and 2022, and 2023."
At the moment, Lowcock said, the actions of the richer world risk prolonging the crisis, rather than ending it.
"If the phasing [of the vaccine] is simply who shouts the loudest and pays the most, that will end up with an outcome that is not rational for the world as a whole, because it will leave great reservoirs of Covid, that then threaten to come back and get everybody," he said.
Modelling by Northeastern University published in September also found that, if rich countries buy up the first two billion doses of vaccines instead of distributing them in proportion to the global population, almost twice as many people could die from Covid-19.
While there has been some positive news on vaccines recently - for example, an initiative to get them to the world's poorest has secured the two billion doses it needs - huge financial holes remain and there are major distribution hurdles.
There are also big funding gaps for some of the world's most pressing humanitarian crises - despite record commitments that will bring the total pledged this year to around US$20 billion (£15bn) - Lowcock added.
Against this backdrop, he described the UK aid cut last year as "regrettable".He has warned that famine - previously almost eradicated - is looming for several countries.
There was a similar situation in a number of places in 2017, he said, and major disaster was largely averted because the humanitarian effort was well-funded. That is not the case now, with a record funding gap of US$22bn.