Pfizer slashed in half the volume of Covid-19 vaccines the company will deliver to some EU countries this week, government officials said, as frustration over the U.S. drugmaker’s unexpected cut in supplies grows.

Europe launched a cross-border vaccination program of unprecedented scale on Dec. 27 as part of efforts to end the Covid-19 pandemic that has crippled economies and claimed more than 1.7 million lives around the world.