Employees at an Emergent BioSolutions (NYSE:EBS) facility in Baltimore made a mistake several weeks ago when formulating the ingredients for Johnson & Johnson’s COVID-19 vaccine, requiring 15 million doses of it to be discarded.

A quality control process revealed that one batch of a drug substance for the J&J COVID-19 vaccine “did not meet quality standards,” according to a statement from Johnson & Johnson.

The batch did not reach the fill-and-finish stage of manufacturing.

Emergent BioSolutions is a contract manufacturer for both Johnson & Johnson (NYSE:JNJ) and AstraZeneca (LON:AZN).

The mistake could delay the FDA’s authorization of Emergent BioSolutions production lines for the Johnson & Johnson COVID-19 vaccine.

The error also led Johnson & Johnson to increase its oversight over the vaccine production at the Emergent BioSolutions site.

Current shipments of J&J vaccines, which were produced in the Netherlands, remain unaffected.

Robert Kramer, Emergent BioSolutions president and CEO, stressed that the error was not a result of a mixing of ingredients of vaccines from Johnson & Johnson and AstraZeneca, as the Washington Post and others had reported.  “It wasn’t the case where an ingredient from one vaccine contaminated or impacted another,” Kramer told CNBC. “It was more simply the fact that one production run — one batch of product — was determined to be inconsistent with our quality specifications.”

Johnson & Johnson still expects to produce more than one billion doses of the COVID-19 vaccine by the end of the year.

Emergent BioSolutions was also the focus of a recent exposé from The New York Times, which described its efforts to lobby the U.S. government to buy millions of anthrax vaccine doses. As a result, the paper argued, the U.S. had relatively little money left over for pandemic response.