The Biden administration said Sunday that the country will have sufficient coronavirus vaccine doses to meet the president’s goal of enabling every adult in the United States to get immunized by the end of May, despite the contamination of millions of doses at a troubled Baltimore manufacturing facility.

A senior administration official, who spoke on the condition of anonymity to discuss the sensitive matter, said health officials had negotiated for more than a week for an arrangement, announced late Saturday, under which Johnson & Johnson would take over responsibility for manufacturing at the plant.

Johnson & Johnson developed one of the two coronavirus vaccines being made at the Baltimore facility where the cross-contamination occurred.

Federal officials were working over the weekend to pin down another U.S. site where the other vaccine produced at the facility — one developed by AstraZeneca — could be manufactured and already have identified potential locations.

Meanwhile, the company that owns the plant, Emergent Bio­Solutions, may be allowed to retain some of its employees in making the Johnson & Johnson vaccine, as long as it relinquishes full control of the manufacturing and quality inspections, the official said. Emergent BioSolutions is a major government contractor.

The developments followed the news that a batch amounting to 15 million doses of Johnson & Johnson’s vaccine were spoiled at the Emergent plant after being contaminated with ingredients for the AstraZeneca vaccine.

The error was caught, and no contaminated vaccine left the plant, according to the companies involved. No doses had shipped because the plant has not yet been certified by the Food and Drug Administration as a manufacturer of coronavirus vaccine.

When President Biden took office in January, his administration inherited a scarcity of the two vaccines that the FDA had by then authorized for emergency use against the novel coronavirus. Those vaccines were developed by Pfizer-BioNTech and Moderna. Johnson & Johnson’s was authorized in late February.

The president and his aides have made ramping up vaccine supplies a priority. A month ago, Biden pledged that stepped-up vaccine manufacturing would lead to enough doses by the end of May for every adult who wanted to be vaccinated.

On Sunday, the senior official said that, no matter what happens with the Baltimore plant or the manufacture of the AstraZeneca vaccine, which is not authorized for U.S. use, “there is enough vaccine for all adult Americans who want it by May 31.”

Federal rules specify that multiple “live vector” vaccines should not be made in the same place, but the official said it had been ambiguous whether the rule applies to the type of vaccines developed by Johnson & Johnson and by AstraZeneca, or whether two vaccines could be made in separate areas of a plant. “They proved they can’t,” the official said.

That official and two other administration officials who also spoke on the condition of anonymity to discuss the sensitive situation said that, in deciding which vaccine should continue at the Emergent facility, the Department of Health and Human Services chose to keep Johnson & Johnson because those shots could be used in the United States, as soon as the FDA certifies the plant for that use.

According to the officials, the Biden administration negotiated a path out of the plant’s contamination troubles without explicitly invoking the Defense Production Act, a 1950s-era law that has been used to accelerate vaccine-making material and other virus-fighting supplies.

Johnson & Johnson said in a statement Saturday that it “is adding dedicated leaders for operations and quality, and significantly increasing the number of manufacturing, quality and technical operations personnel to work with the company specialists already at Emergent.”

The company said it still expected to deliver 100 million doses of its single-shot vaccine to the U.S. government by the end of May.

Emergent spokeswoman Nina DeLorenzo said the company intends to stop making the AstraZeneca vaccine in the next few days.

AstraZeneca said in a statement that it is working with the federal government “to support agreed-upon plans for the development, production and full delivery of the vaccine.”

AstraZeneca did not say how much its departure from the Emergent plant could set back its manufacturing timeline in the United States. It has taken other manufacturers six months or more to ramp up new supplies of coronavirus vaccine lines.

Unrelated to the contamination by Emergent employees, ­AstraZeneca already has been beset by problems with clinical trials, controversy over reporting of its data, and concerns in Europe about blood clots as a rare side effect. In May, the company predicted that it would begin delivering the first of 300 million doses of its vaccine for the United States in the fall, but it did not meet that ambitious goal, nor has the FDA authorized it for emergency use.

For Emergent to spoil raw vaccine substance amounting to 15 million doses suggests a significant breakdown in quality control at early stages of manufacturing that should have been caught in subsequent steps, said John Avellanet, an FDA compliance expert who is managing director at the consulting firm Cerulean Associates.

If contamination had been detected earlier in the process, he said, it probably would have affected far less product. Johnson & Johnson had said last year that Emergent would be making vaccine in single-use, 1,000-liter bioreactor bags. The magnitude of this incident indicates that more than one bag’s product was probably affected, Avellanet said, adding that it was highly unusual for so much vaccine substance to be ruined in one incident.

The changes in vaccine production at the plant were first reported Saturday by the New York Times.

The Washington Post reported last week that an FDA investigator flagged problems at the Baltimore facility six weeks before the Trump administration announced a $628 million deal with Emergent as part of Operation Warp Speed, the government’s program at the time to develop and produce vaccines to fight the virus.

Emergent secured deals totaling more than $740 million with Johnson & Johnson and AstraZeneca to produce vaccines at the Baltimore site.

The Post reported last year that Emergent had benefited from billions of dollars in federal contracts as health officials directed public spending toward the threat of bioterrorism attacks at the expense of some preparations for a pandemic.

Emergent’s Warp Speed deal was made as part of a long-standing contract between the company and the agency within HHS responsible for preparing for public health threats.

At the time of the award, that agency was led by Assistant Secretary Robert Kadlec. The Post previously reported that before joining the Trump administration, Kadlec was paid as a consultant to Emergent and formed a start-up company with Emergent’s chairman. Kadlec did not mention either role in a questionnaire about his career that he completed for the Senate when it considered his nomination by Trump in 2017. Kad­lec and Emergent previously told The Post that Kadlec’s past work for Emergent had no bearing on the firm’s government contracts.

Laurie McGinley contributed to this report.