The United States has put Johnson and Johnson in charge of a plant that ruined 15 million doses of its COVID-19 vaccine and has stopped British drugmaker AstraZeneca Plc from using the facility, a senior health official said on Saturday.

J&J said it was "assuming full responsibility" of the Emergent BioSolutions facility in Baltimore, reiterating that it will deliver 100 million doses to the government by the end of May.

The Department of Health & Human Services facilitated the move, the health official said in an email, asking not to be named due to the sensitivity of the matter.

AstraZeneca, whose vaccine has not been approved in the United States, said it will work with President Joe Biden's administration to find an alternative site to produce its vaccine.

White House officials did not immediately respond to a request for comment.

The development, first reported by the New York Times, further hampers AstraZeneca's efforts in the United States. The government has criticized the drugmaker for using outdated data in the results of its vaccine trial. It later revised its study.

Workers at the Emergent BioSolutions plant several weeks ago conflated ingredients for the J&J and AstraZeneca vaccines, the Times said earlier in the week. J&J said at the time the ruined batch had not advanced to the fill-and-finish stage.

The government's move to have the facility make only the J&J single-dose vaccine is meant to avoid future mix-ups, the Times said, citing two senior federal health officials.

The top US infectious disease doctor told Reuters on Thursday the country may not need AstraZeneca's vaccine even if it wins approval.

The United States has loan deals to send Mexico and Canada roughly 4 million doses of the AstraZeneca vaccine, made at its US facility.