A shortfall in Moderna’s vaccine doses from its European suppliers means deliveries to Canada and the UK have been delayed.

The drugmaker said it will deliver approximately 650,000 doses by the end of April, not the expected 1.2m, Canada’s procurement minister Anita Anand said.

Additionally one to two million Moderna doses of the 12.3m doses expected for the second quarter would be delayed until the third.

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Shipments to the UK will start being reduced this month just days after it was rolled out alongside the Astrazeneca and Pfizer vaccines. It has purchased 17m doses of the Moderna vaccine, its smallest contract so far.

Moderna is working with Swiss company Lonza Group to make the vaccines for Europe and said the slowdown was due to limited production capacity.

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The reduced deliveries will do little to quell concerns over global vaccine supplies, which have been exacerbated by concerns about a link to rare clots. It has prompted restrictions on the rollout of both the Astrazeneca and Johnson & Johnson jabs.

“The trajectory of vaccine manufacturing ramp up is not linear, and despite best efforts, there is a shortfall in previously estimated doses,” Moderna said.

“Vaccine manufacturing is a highly complex process and a number of elements, including human and material resources, have factored into this volatility.”