AstraZeneca has been kicked out of a production plant in Baltimore after a mix-up is thought to have contaminated 15 million doses of a coronavirus vaccine produced by Johnson & Johnson.
The Oxford/AstraZeneca jab has yet to obtain approval from the US Food and Drug Administration, but production of the vaccine has started in anticipation of a green light.
It was being produced by a sub-contractor at a plant operated by Emergent BioSolutions in Baltimore.
The plant was also manufacturing Johnson & Johnson's vaccines and workers at the factory mistakenly mixed the ingredients.
As a result 15 million doses of the vaccine produced by Johnson & Johnson, which has been given FDA approval, had to be destroyed.
Johnson & Johnson will now assume full responsibility for the production of its vaccine at the plant.
The pharmaceutical giant, which has promised to deliver 100 million doses of its single-shot vaccine to the US by the end of May, said it will deploy additional staff at the Baltimore plant.
AstraZeneca's vaccine will be produced elsewhere in the United States, the US Department of Health and Human Services said. The location has not been disclosed.
"AstraZeneca and the US Government continue to work closely together to support agreed-upon plans for the development, production and full delivery of the vaccine," the company said.
The American decision is a fresh blow for the Anglo-Swedish company after Germany suspended the use of the AstraZeneca vaccine for the under-60s last week because of concerns over reported blood clots.
Other European countries have also paused use of the vaccine in recent weeks amid safety concerns.
The European medicines Agency has said the AstraZeneca vaccine is "safe and effective" with the benefits outweighing the risks.
Anthony Fauci, America's top infectious diseases expert, has voiced doubts that the United States would even need the AstraZeneca vaccine given the contracts which have already been signed with other manufacturers.
"My general feeling is that given the contractual relationships that we have with a number of companies, that we have enough vaccine to fulfill all of our needs without invoking AstraZeneca," he said last week.
“If you look at the numbers (of doses) that we’re going to be getting … it is likely that we can handle any boost that we need, but I can’t say definitely for sure,” he told Reuters.