The drugmaker didn't say how many doses were lost, and it wasn't clear how the problem would impact future deliveries.
The company said quality control identified one batch of drug substance that did not meet quality standards at Emergent Biosolutions, and that batch was never advanced to the filling and finishing stages of its manufacturing process.
J&J has met its goal to ship 20 million doses to the US government by the end of March, the company said in its statement. While more than 1.3 million people are fully vaccinated, the state has reported lower vaccination levels among Latino and Black residents, even in predominantly nonwhite cities such as Springfield.
A federal official said Wednesday evening the administration's goal can be met without additional J&J doses.
As of Wednesday, almost 4 million Pennsylvania residents have received at least one dose of the vaccine.
Timeline: China's cooperation with World Health Organization on COVID-19 origins study
Transmission of SARS-CoV-2 from an animal reservoir like bats to another host in which the virus spread before infecting humans. Repeated delays in the report's release raised questions about whether the Chinese side was trying to influence the findings.
It was not immediately clear where those 11 million doses originated, but J&J has been shipping finished vaccines from its factory in the Netherlands to the U.S.
Employees at Emergent BioSolutions, a production facility in Baltimore, reportedly mixed-up two vaccine dosages. "This approach includes having dedicated specialists on the ground at the companies that are part of our global manufacturing network to support safety and quality".
Gov. Charlie Baker said the federal government plans to distribute 5 million doses of the COVID-19 vaccine developed by Johnson & Johnson across the country next week.
"Our deliveries of J&J will be beginning at the end of April", she said during a press conference on Tuesday. Only 3.3 million doses have been administered, CDC data show. The company also has pledged to sell the vaccine without a profit, but only during the pandemic emergency.
The FDA told AFP it was "aware of the situation" but declined to comment further.