Because the shot uses cell lines descended from those taken from aborted fetuses four decades ago.
Catholic Bishops are advising people against getting one of the Covid vaccines because of its connection to aborted fetuses.
The U.S. Conference of Catholic Bishops released a statement on Tuesday raising issues with the Johnson & Johnson shot in particular.
"The approval of Johnson & Johnson's COVID-19 vaccine for use in the United States again raises questions about the moral permissibility of using vaccines developed, tested, and/or produced with the help of abortion-derived cell lines," it said.
According to Bishop Kevin C. Rhoades, chairman of the Committee on Doctrine, and Archbishop Joseph F. Naumann, chairman of the Committee on Pro-Life Activities, Pfizer and Moderna's vaccines raised concerns because an abortion-derived cell line was used for testing them — but not in their production, like the J&J one.
They said that the Congregation for the Doctrine of the Faith had judged "when ethically irreproachable Covid-19 vaccines are not available … it is morally acceptable to receive Covid-19 vaccines that have used cell lines from aborted fetuses in their research and production process."
However, if people have a choice between vaccines, they should go for the least abortion-connected one.
"Therefore, if one has the ability to choose a vaccine, Pfizer or Moderna's vaccines should be chosen over Johnson & Johnson's," it said.
"While we should continue to insist that pharmaceutical companies stop using abortion-derived cell lines, given the world-wide suffering that this pandemic is causing, we affirm again that being vaccinated can be an act of charity that serves the common good," it added.
None of the vaccines actually contain fetal tissue. Fetal cell lines are cells that are grown in a laboratory, that are descended from cells taken from fetal tissue from elective abortions all the way back in the 1970s and 1980s; they are thousands of generations removed from the original tissue.
Scientists need to test the vaccines on these lab grown cells to ensure they work, and that they are safe.