Johnson & Johnson vaccine was contaminated by ingredients from another company’s vaccine at a manufacturing plant in Baltimore, federal officials confirmed Wednesday, ruining a batch of raw vaccine representing millions of doses and prompting a review.

However, Johnson & Johnson said in a statement that it was still on track to deliver the 20 million doses it promised the federal government by Wednesday, as well as another 24 million doses by the end of April.

The mixing of ingredients for coronavirus vaccines from Johnson & Johnson and AstraZeneca occurred at a plant operated by Emergent, which has not yet been certified by the Food and Drug Administration to produce the Johnson & Johnson vaccine.

Emergent is a contract manufacturer for bulk vaccine substance for drugmakers Johnson & Johnson and AstraZeneca. It also has federal agreements for the production of medicines to combat bioterrorism threats.

Emergent issued a statement about the mix-up on Thursday.

“There are rigorous quality checks throughout our vaccine manufacturing processes, and through these checks a single batch of drug substance was identified that did not meet specifications and our rigorous quality standards. We isolated this batch and it will be disposed of properly,” the company said. “Importantly, the quality control systems worked as designed to detect and isolate this single batch.”

Federal officials reported a number of production problems at the Emergent BioSolutions plant in Baltimore, including contaminated vaccines and poor sanitation. (Reuters)

It noted that discarding batches occasionally happens during vaccine manufacturing. It said it remains confident it can meet its commitments to Johnson & Johnson and AstraZeneca, as well as the federal government, which spent $628 million to reserve capacity and make upgrades to Emergent’s plant.

Discarding a batch of bulk drug substance, while disappointing, does occasionally happen during vaccine manufacturing, which is a complex and multi-step biological process.

Johnson & Johnson’s vaccine was granted emergency-use authorization by the FDA in February. After a number of clinical trial problems, AstraZeneca’s vaccine, a collaboration with University of Oxford researchers, has not yet been authorized in the United States.

None of the contaminated vaccine made it out of the plant, according to a federal official who was not authorized to discuss the matter. It had not reached the “fill-and-finish” stage of production, which involves final formulation and filling vials after bulk vaccine is shipped to a Catalent plant in Indiana.

“We are going to make sure that we understand what happened,” said a health official, who spoke on the condition of anonymity because he was not authorized to discuss the situation. “We have to work through and find out what is going on.”

Johnson & Johnson provided no details in a statement but said it was beefing up staff and oversight of vaccine manufacturing at the plant in Baltimore.

It has been shipping raw ingredients from Europe pending certification of the Emergent facility.

“Johnson & Johnson is providing additional experts in manufacturing, technical operations and quality to be on-site at Emergent to supervise, direct and support all manufacturing of the Johnson & Johnson coronavirus vaccine,” the company said in a statement.

The New York Times first reported the incident. It said that about 15 million doses were ruined and that federal officials had attributed it to human error.

Johnson & Johnson did not confirm the estimate of the volume that was ruined, but at Johnson & Johnson’s $10-a-dose price for the finished product, the value would be up to $150 million.

The federal official said the cross-contamination was caught on routine quality-control checks by Johnson & Johnson. “The issue is whether manufacturing processes at the plant are suboptimal,” said the official. “Nothing got out of the plant.”

The discovery was made a few days ago, setting off a flurry of meetings involving the FDA, Johnson & Johnson and the Biomedical Advanced Research and Development Authority in the Department of Health and Human Services.