BRUSSELS -- A shipment of more than a quarter million AstraZeneca vaccines destined for Australia has been blocked from leaving the European Union, in the first use of an export control system instituted by the bloc to make sure big pharma companies would respect their contracts.

The move, affecting only a small number of vaccines, underscores a growing frustration within the 27-nation bloc about the slow rollout of its vaccine drive and the shortfall of promised vaccine deliveries, especially by Anglo-Swedish AstraZeneca.

The ban came at the behest of Italy, and the EU did not raise objections to the tougher line Rome has adopted in dealing with vaccine shortages in the bloc since a new government led by Mario Draghi came into power Feb 13.

Australian Prime Minister Scott Morrison told reporters on Friday it had anticipated veto problems could arise in shipments from Europe, adding that Australia's inoculation schedule would continue as planned.

"They are in an unbridled crisis situation. That is not the situation in Australia," Morrison said. "But, nevertheless, we have been able to secure our supplies, and additional supplies for importation, both with Pfizer and AstraZeneca, which means we can continue the rollout of our program."

He said most significantly, Australia was also producing vaccines domestically, giving it sovereignty over its vaccination program.

Italy's objections centred both on the general shortage of supplies in the EU and on "the delays in the supply of vaccines by AstraZeneca to the EU and Italy," a Foreign Ministry statement said.

It said it also intervened because of the size of the shipment, more than 250,700 doses, that would go to Australia, which it did not consider a vulnerable nation.

Italy said it had informed the company on Tuesday. AstraZeneca refused to comment. The Financial Times first reported on the issue late Thursday.

Faced with shortages of doses during the early stages of the vaccine campaign that started in late December, the EU issued an export control system for COVID-19 vaccines in late January, forcing companies to respect their contractual obligations to the bloc before commercial exports can be approved.

The EU has been specifically angry with AstraZeneca because it is delivering far fewer doses to the bloc than it had promised. Of the initial order for 80 million doses to the EU in the first quarter, the company will be struggling to deliver just half that quantity.

There were rumours that the company was siphoning off from EU production plants to other nations, but CEO Pascal Soriot insisted that any shortfall was to be blamed on technical production issues only.

The EU has vaccinated only 8% per cent of its population compared to over 30%, for example, in the United Kingdom. Australia is still very much at the start of its vaccination drive.

With such an action, the EU is caught in a bind. On the one hand, it is under intense pressure to ramp up the production of vaccines in the bloc while on the other hand it wants to remain an attractive hub for pharmaceutical giants and a fair trading partner to third countries.

The EU thought it had made perfect preparations for the rollout of vaccinations, heavily funding research and production capacity over the past year. With its 450 million people, the EU has signed deals for six different vaccines. In total, it has ordered up to 400 million doses of the AstraZeneca vaccine and sealed agreements with other companies for more than 2 billion shots.

It says that despite the current difficulties it is still convinced it can vaccinate 70% of the adult population by the end of summer.

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Danica Kirka contributed from London, Colleen Barry from Milan, and Nick Perry from Wellington, New Zealand.