AstraZeneca did not immediately respond to a request for comment.
Officials said they asked AstraZeneca for additional information on where the active ingredient in the vaccine vials found in Italy was made – a question aimed at forcing the company to provide more information on its chain of supply and production capacity.
For AstraZeneca, the Italian dose dispute was the latest in a series of communication blunders with health officials on both sides of the Atlantic that have affected the company’s relationships with multiple governments.
Some US officials learned of a snag in the company’s clinical trials from the media last year. The company’s U.S. trial was suspended for nearly seven weeks last fall, in part because AstraZeneca was slow to provide U.S. regulators with proof that the vaccine did not cause neurological disease. (Investigators later concluded that the symptoms were unrelated to the vaccine.)
But analysts believe some of AstraZeneca’s manufacturing difficulties also reflect the company’s ambitious global distribution plans. It intended to manufacture up to three billion doses this year, in part by outsourcing its manufacture to factories around the world. Other vaccine manufacturers, on the other hand, rely on only a few facilities.
This global network of factories has the potential to create complications in the company’s supply chain, analysts say, although it is also part of what made the vaccine so essential to the global effort to vaccination.
Benjamin mueller contributed reporting from London.