THE European Union’s dispute with AstraZeneca over vaccine supplies has intensified as the drugmaker defended itself against claims that it had reneged on contractual commitments and the two sides sparred over plans for further talks.

AstraZeneca chief executive Pascal Soriot addressed the dispute for the first time, rejecting the EU’s assertion that the company was failing to honour its commitments to deliver coronavirus vaccines.

He said delivery figures in AstraZeneca’s contract with the EU were targets, not firm commitments, and they could not be met because of problems in rapidly expanding production capacity.

“Our contract is not a contractual commitment,” Mr Soriot said in an interview with Italian newspaper La Repubblica. “It’s a best effort. Basically we said we’re going to try our best, but we can’t guarantee we’re going to succeed. In fact, getting there, we are a little bit delayed.”

After the interview was published, an EU spokeswoman said AstraZeneca had pulled out of talks on Wednesday about problems with vaccine supplies, which AstraZeneca immediately denied. Hours later, the EU said the talks were back on.

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The EU, which has 450 million citizens and the economic and political clout of the world’s biggest trading bloc, is lagging badly behind countries such as Israel and Britain in rolling out coronavirus vaccine shots for its healthcare workers and most vulnerable people. That is despite having more than 400,000 confirmed virus deaths since the pandemic began.

The spat has also raised concerns about vaccine nationalism, as countries desperate to end the pandemic compete for limited supplies of the precious vaccine shots. On Monday, the 27-nation bloc threatened to put export controls on all vaccines made on its territory.

The EU has signed deals to get access to six different vaccines, but so far has only approved ones by Pfizer-BioNTech and Moderna. The EU’s drug regulator will consider the Oxford-AstraZeneca vaccine on Friday.

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AstraZeneca said last week that it planned to cut initial deliveries in the EU to 31 million doses from 80 million due to reduced yields from its manufacturing process in Europe. That drew an angry response from the EU, which says it expects the company to deliver the full amount on time.

AstraZeneca is setting up more than a dozen regional supply chains worldwide to meet regional demand for its vaccine. Overall, AstraZeneca plans to deliver up to three billion doses to countries around the world by the end of 2021.

However, establishing each facility is a complicated process that involves training people and ensuring each batch of vaccine is safe and effective. Sometimes this goes smoothly, but in other cases there are problems, Soriot said.

“We train them on how to manufacture,″ he said. “And then, you know, some people are new to this process. It’s like they learn the process. They don’t know how to make the vaccine and they’re not as efficient as others.″ There are two basic steps in producing the vaccine. The first is a biological process that involves growing cells, which are injected with a virus, Mr Soriot said. The second involves turning this “drug substance” into the final product, filling vials and testing each batch of vaccine.

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Soriot said AstraZeneca had to reduce deliveries to the EU because plants in Europe had lower than expected yields from the biological process used to produce the vaccine. This has also happened in other regions as AstraZeneca sought to rapidly expand production capacity to meet demands from countries battling the pandemic.

“We’ve also had teething issues like this in the UK supply chain,” Mr Soriot said. “But the UK contract was signed three months before the European vaccine deal, so with the UK we have had an extra three months to fix all the glitches we experienced. As for Europe, we are three months behind in fixing those glitches.”

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The shortfall of planned deliveries of the AstraZeneca vaccine is coming at the same time as a slowdown in the distribution of Pfizer-BioNTech shots as Pfizer upgrades production facilities at a plant in Belgium.

“There are a lot of emotions running in this process right now, and I can understand it: people want the vaccine. I want the vaccine too, I want it today,″ Soriot said. “But, at the end of the day, it’s a complicated process.″