(Bloomberg) -- Hundreds of millions of Covid-19 vaccine doses purchased by wealthy countries are at risk of going to waste, a new analysis shows, while large parts of the world remain unprotected amid the spread of the omicron variant.

About 240 million doses purchased by the U.S., U.K., Japan, Canada and the European Union are expected to go unused and expire by March, London-based analytics firm Airfinity Ltd. said Thursday in a report. The number of potentially wasted doses could climb to 500 million by that point if other countries receiving donated doses don’t have enough time to administer them, it said.

“Even after successful booster rollouts, there are surplus doses available that risk going to waste if not shared very soon,” Rasmus Bech Hansen, Airfinity’s chief executive officer, said in a statement. “The emergence of omicron and the likelihood of future variants shows there is no time to waste.”

Squandering doses of precious Covid vaccine threatens to exacerbate shortfalls, especially in Africa and other parts of the developing world. Donated supplies often arrive with little notice and short shelf lives, making it even harder for stretched health systems in poorer countries to turn them into inoculations.

As shipments ramp up for billions of people left behind last year, health groups have been calling for donated doses to be delivered in a more reliable and predictable way. The stakes are rising as omicron drives case counts higher even in rich countries like the U.S., where the variant accounts for about 98% of new sequenced cases. 

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