As officials and health experts race to get Americans vaccinated against Covid-19, some Catholic bishops have weighed in to discourage Church members from getting the latest, single-shot vaccine from Johnson & Johnson when alternatives are available.

The US Conference of Catholic Bishops, as well as at least 6 other dioceses from across the country have released statements expressing "moral concerns" over the shot due to its use of lab-grown cells that descend from cells taken in the 1980s from the tissue of aborted fetuses.

The vaccine is the third to be authorized for use in the United States. Unlike its predecessors – from Pfizer/BioNTech and Moderna – the Johnson & Johnson vaccine requires only one shot and can be kept at normal refrigerator temperatures, making it easy to transport.

Health experts have cautioned that Americans should get the vaccine they are offered.

“If people are offered the Johnson & Johnson vaccine, they shouldn’t say, ‘I don’t want it’,” Dr. Paul Goepfert, director of the Alabama Vaccine Research Clinic, said last month. “We are not in a scenario where we can pick and choose vaccines.”

Prior to the US emergency use authorization for the Johnson & Johnson vaccine, the doctrinal office for the Roman Catholic Church – the Congregation for the Doctrine of the Faith – said that “it is morally acceptable to receive Covid-19 vaccines that have used cell lines from aborted fetuses in their research and production process.”

The new statement from the Conference of Bishops is at odds with a note approved by Pope Francis, who received a vaccine in January. The December note said that “the use of such vaccines does not constitute formal cooperation with the abortion from which the cells used in production of the vaccines derive.”

In a statement to CNN, Johnson & Johnson said: “We are proud to bring our COVID-19 vaccine to the world and to contribute to ending this pandemic. Our single-shot COVID-19 vaccine uses an inactivated non-infective adenovirus vector – similar to a cold virus – that codes for the coronavirus “spike” (S) protein, and there is no fetal tissue in the vaccine.

“We are able to manufacture hundreds of millions of doses using our engineered cell-line system and look forward to delivering those doses around the world and help meet the critical need.”

The White House on Wednesday pushed back on the statement from the Conference of Bishops.

An administration official pointed CNN toward the Vatican statement from December, adding that the Biden administration is also “addressing hesitancy and working with local messengers on how to address that, including with religious leaders.”

President Joe Biden is a practicing Catholic. (CNN)