Emergent BioSolutions said Thursday it has received the go-ahead from the Food and Drug Administration to resume manufacturing Johnson & Johnson coronavirus vaccine after a suspension of more than 100 days because of cross-contamination at its Baltimore factory.

The company still does not have full FDA approval that would allow any bulk vaccine produced there to be distributed in the United States without additional reviews, but the company called the restart an important step toward getting the only domestic source of Johnson & Johnson’s single-shot vaccine back on track.

The plant has been shut down since April after it was discovered a month earlier that Johnson & Johnson vaccine had been contaminated by a different vaccine also being made at the plant for AstraZeneca.

The AstraZeneca vaccine, which is not approved for use in the United States, was removed from the facility, and Emergent has spent the last three months cleaning the plant and correcting myriad problems. A scathing FDA inspection report on the Emergent plant in April cited unsanitary conditions and a lack of adherence to basic protocols intended to prevent contamination of the vaccine. At least 75 million doses worth of Johnson & Johnson vaccine have been discarded.

The FDA has cleared bulk vaccine made at the plant representing up to 50 million doses based on batch-by-batch reviews, Bloomberg reported on July 13, but where those doses will be sent has not been disclosed. Johnson & Johnson and the Department of Health and Human Services did not respond to questions Thursday about where the doses would be sent.

"We will continue to work toward securing Emergency Use Authorization in the United States for drug substance manufactured at Emergent Bayview as quickly as possible,'' Johnson & Johnson said in an emailed statement.

The Biden administration has said it plans to send some vaccines made in the United States to countries that desperately need it.

“The American people should have high expectations of the partners its government chooses to help prepare them for disaster, and we have even higher expectations of ourselves,” Emergent chief executive Robert Kramer said in a news release Thursday.

“We have fallen short of those lofty ambitions over the past few months but resumption of manufacturing is a key milestone and we are grateful for the opportunity to help bring this global pandemic to an end,'' he said.

The supply of the Johnson & Johnson vaccine has fluctuated. About 21 million doses have been delivered throughout the United States, of which about 13 million have been administered, according to Centers for Disease Control and Prevention data. They were imported from the company’s operation in the Netherlands. No shots from the Emergent plant have been distributed in the United States.

Demand for Johnson & Johnson vaccine in the United States has lagged behind after the CDC suspended use of the shots for nine days in April in response to a side effect of very rare blood clots.

The amount of Johnson & Johnson vaccine administered domestically compares with about 330 million shots administered in the United States of the two-dose vaccines made by Pfizer and Moderna.