The halt is temporary, with the plant in the Dutch city of Leiden expected to start making the vaccine again after a few months.
The plant has instead been making an experimental but potentially more profitable vaccine to protect against an unrelated virus.
J&J currently has millions of doses of its Covid-19 vaccine in inventory, the company said in an email, adding that it continues to provide all its fill-and-finish sites with drug substance required to produce its shot.
"We continue to fulfill our contractual obligations in relation to the COVAX facility and the African Union," J&J said.
With the Leiden plant temporarily unavailable, it could reduce the supply of the J&J vaccine by a few hundred million doses.
Other facilities have been tapped to manufacture the vaccine but they are either not up and running or are yet to receive regulatory approval to make the shot, the report added.