Johnson & Johnson has admitted to having produced a faulty batch of coronavirus vaccines at an East Baltimore facility, reportedly due to a mix-up of two ingredients that led to the ruining of about 15 million doses.

“As with the manufacturing of any complex biologic medication or vaccine, the start-up for a new process includes test runs and quality checks to ensure manufacturing is validated and the end product meets our high-quality standards”, Johnson & Johnson said on Wednesday,

“This quality control process identified one batch of drug substance that did not meet quality standards at Emergent Biosolutions. “This batch was never advanced to the filling and finishing stages of our manufacturing process”, the vaccine manufacturer said.

According to Johnson & Johnson, the issue was addressed with the Emergent Biosolutions manufacturing plant in East Baltimore and shared with the US Food and Drug Administration (FDA).

Johnson & Johnson’s single-shot coronavirus vaccine was approved for emergency use in the US at the end of February, becoming the third vaccine to be authorised by the FDA (in addition to the Pfizer/BioNTech and Moderna COVID-19 vaccines).