By Carl O’Donnell

(Reuters) – An estimated 30 million to 50 million doses of Johnson & Johnson (NYSE:)’s COVID-19 vaccine made early this year sits idle in Emergent BioSolutions Inc’s plant in Baltimore awaiting a green light from U.S. regulators to ship, two sources familiar with the matter said.

Emergent is a contract manufacturer of drugs and has been waiting for approval from the U.S. Food and Drug Administration. One source said that the agency still needs to inspect the facility and authorise Emergent before it can ship new drug substances.

Sources cannot determine the exact number of unfilled doses because Emergent doesn’t make any finished products and only produces raw vaccine substances.

The FDA in April halted operations at Emergent’s production facility after J&J’s vaccine was found to be contaminated with material from AstraZeneca (NASDAQ:)’s COVID-19 shots, which were also being manufactured there at the time.

The contamination ruined about 15 million J&J doses and set back its U.S. vaccine rollout by weeks.

Material manufactured for the J&J vaccine at the Baltimore plant prior to the April shutdown and awaiting FDA approval could be enough to produce as many as 50 million shots, the two sources said. The two sources requested anonymity because they are not allowed to talk publicly about the subject.

Of the 100 million doses worth of vaccine material Emergent described in an April Congressional hearing as being sidelined, the FDA has so far cleared nine batches of J&J’s vaccine and three batches of AstraZeneca’s. However, it hasn’t disclosed the number of doses in those batches.

Emergent in late July said it would resume production of J&J’s vaccine at the plant following additional FDA reviews, but has not provided updates on production or timing of potential shipments. [L1N2P535Q]

One source said that Emergent is now producing new vaccine substances, although the FDA has not yet provided guidance as to when they will inspect the Baltimore facility.

In a statement, the FDA stated that it carried out a small inspection at Emergent’s plant in July in order to verify it had taken corrective action following April’s production pause. The previous inspection revealed a host of issues in the facility’s sanitary and safety practices.

Although the agency has yet not authorized the facility for shipment of doses, the agency continues to monitor batches that were made before the production halt. The agency has used facility records reviews and quality testing to approve batches.

A former FDA official said that the FDA waits to inspect a manufacturing plant before it produces multiple batches. This is because they are not allowed to talk to the media.

Following the Emergent plant shutdown, J&J lowered its production target for 2021 to between 500 million and 600 million doses from around 1 billion. The company expects to produce 1 billion doses per year starting in the next year.

J&J has not specified whether it needs Emergent to restart production to hit its 2022 target. There is a second manufacturing plant in Leiden, Netherlands. It also has production agreements with several other contract producers, such as Catalent Inc (NYSE:) Inc, and India’s Biological E.

The United States contracted with J&J for 100 million shots in 2020 and ordered an additional 100 million in March.

Last week, the FDA authorized J&J’s vaccine as a booster for people who are already vaccinated but desire additional protection against COVID-19, including anyone over age 18 who originally received the company’s single-dose shot.

Use of J&J’s vaccine fell sharply in the United States after it was linked to a rare but potentially lethal blood clotting disorder.