The batch of bulk drug substance – which has not yet been put into vials – can make up to 15 million doses of J&J’s vaccine, according to a source familiar with the matter.

The FDA has now authorised a total of four batches of the vaccine manufactured at the Emergent facility.

“While the FDA is not yet ready to include the Emergent BioSolutions plant … as an authorised manufacturing facility, the agency continues to work through issues there with Janssen and Emergent BioSolutions management,” the agency said in a statement, referring to J&J’s pharmaceuticals unit.

Production of J&J’s vaccine at the Baltimore site was halted by US authorities in April following the discovery that ingredients from AstraZeneca’s Covid-19 vaccine, also being produced at the plant at the time, contaminated a batch of J&J’s vaccine.

An FDA inspection of the plant also turned up a long list of sanitary problems and bad manufacturing practices.

“As Covid-19 continues to impact countries and cause untold suffering worldwide, we remain committed to producing safe, high-quality vaccines,” J&J said in a statement.

J&J shares closed up about 2% at US$168.98.