A manufacturing error at a plant involved in COVID-19 vaccine production affected 15 million doses worth of an ingredient for Johnson & Johnson’s vaccine, according to two people familiar with the matter, though the company downplayed the situation and said it met its most recent vaccine delivery target.

The issue, which occurred recently at an Emergent BioSolutions Inc. facility in Baltimore, isn’t expected to change President Joe Biden’s expectation that the U.S. will have enough vaccine for all adults in May, the people said.

None of the doses produced and shipped so far in the U.S. have come from that plant, which isn’t authorized yet, two administration officials said, speaking on condition of anonymity.

In a statement, J&J said a batch of drug substance failed its quality test.

Manufacturing problems at the plant were first reported by the New York Times Wednesday. Workers there accidentally conflated ingredients belonging to the J&J vaccine and another manufactured on the premises for AstraZeneca Plc, according to the report. Astra didn’t immediately return calls for comment.

How the issue may affect the U.S. vaccine rollout is unclear. J&J, as of now, has produced by far the smallest supply of the U.S.-authorized COVID-19 vaccines. The two other vaccine producers, Pfizer Inc. and Moderna Inc., met their first quarter targets of 120 million doses and 100 million doses, respectively. Those vaccines require a two-dose regimen.

“This quality control process identified one batch of drug substance that did not meet quality standards at Emergent BioSolutions, a site not yet authorized to manufacture drug substance for our COVID-19 vaccine,” J&J spokesman Jake Sargent said in an emailed statement. “This batch was never advanced to the filling and finishing stages of our manufacturing process.”

The statement added that the drugmaker addressed the issue with Emergent and reported it to the Food and Drug Administration.

The Biden administration has touted J&J’s one-dose, refrigerator-stored COVID shot as an efficient way to confer protection to Americans, particularly those in hard-to-reach places.

Representatives for Emergent declined to comment, deferring to J&J’s statement. The White House declined to comment.

Delivery Target

New Brunswick, New Jersey-based J&J said it beat its March delivery target, providing the U.S. government more than 20 million doses, and that it expects to deliver another 24 million by the end of April. Much of that supply is coming from another contract manufacturer, Catalent Inc., which last week was authorized to make the shot at a facility in Bloomington, Indiana.Read More: J&J Partner Catalent Gets Key U.S. Clearance to Make Vaccine

Biden has set a goal for almost 100 million J&J doses by the end of May, a number that factors into his expectation that the U.S. will have enough vaccine to cover all adults by then.

J&J said Wednesday it still plans to deliver 100 million doses by the end of June, and is “aiming” to deliver them earlier, by the end of May. The problems at J&J’s manufacturing partner suggests that U.S. vaccination goals are vulnerable to events out of the government’s control.

If J&J and other companies met their targets, Biden would have enough doses for 300 million people by then, with just over 260 million adults in the country -- leaving him ample wiggle room to hit his target if any one company falls short.

Johnson & Johnson is now expanding its presence in the Emergent facility, according to the statement. It will provide additional experts in manufacturing, technical operations and quality to be on-site at Emergent to supervise, direct and support the making of its vaccine.

--With assistance from Suzi Ring and Naomi Kresge.