As vaccine mandates have proliferated amid the latest coronavirus surge, so has a divide among the Roman Catholic Church’s U.S. hierarchy over whether their faith provides any basis for congregants to opt out.

The Archdiocese of Philadelphia on Wednesday became the latest to declare a position. In a letter to clergy obtained by The Inquirer, it ordered priests not to assist parishioners seeking religious exemptions, joining some of the nation’s largest Catholic dioceses, including New York and Los Angeles, which have implemented similar policies in recent days.

“Individuals may wish to pursue an exemption from vaccination based on their own reasons of conscience,” wrote the archdiocese’s vicar for clergy, the Rev. Michael F. Hennelly. “In such cases, the burden to support such a request is not one for the local Church … to validate and we are not able to provide support for exemption requests on that basis.”

Yet the decision put the archdiocese at odds with Catholic leaders in other parts of the country, as well as an influential but little-known Philadelphia-based Catholic think tank whose position on the issue has stoked the latest culture-war battle in the U.S. church.

Last month, the National Catholic Bioethics Center — which advises, from a historic mansion in Overbrook, the nation’s bishops and Catholic health-care systems on issues where Catholic teaching and medical science overlap — came out against mandatory vaccination policies in a position paper that laid the groundwork for Catholics to seek religious exemptions.

It even offered a form letter on its website that churchgoers could take to their priest, to endorse their exemption claim.

NCBC president Joseph Meaney, who holds a doctorate in bioethics from the Catholic University of the Sacred Heart in Rome, went further, penning an article that objected to the use of the term vaccine hesitancy and argued many objectors aren’t just “hesitant” but are taking a principled stand against the vaccine.

The basis? All three currently available vaccines used cell lines that originated from fetuses aborted in decades-old procedures in some phase of their development. (Pfizer and Moderna used the cells only to test their vaccines, while Johnson & Johnson deployed them at the research, production, and testing phase, according to the antiabortion Lozier Institute.)

» READ MORE: Why COVID-19 vaccination has become an issue for some who oppose abortion

“At the NCBC, we agree that the best ethical decisions are made ‘in the moment’ based on a good understanding of the facts, when people are not subjected to pressure, or in the grip of powerful emotions,” Meaney wrote. “That is why we do not approve of coercive pressure tactics or vaccine mandates, particularly ones without generous medical, conscience, and religious mandates.”

Reaction to the NCBC’s position came swiftly, with many Catholic scholars noting it seemed to carve out a position counter to the overall thrust of guidance coming from Rome.

Within hours of the think tank’s release of its position paper, the Archdiocese of New York — whose leader, Cardinal Timothy Dolan, sits on the NCBC’s board — told its clergy that “there is no basis for a priest to issue a religious exemption to the vaccine.”

“By doing so he is acting in contradiction to the directives of the Pope and is participating in an act that could have serious consequences to others,” it said in a June 30 memo.

In addition to Philadelphia, New York has since been joined by dioceses including Camden, San Diego, Honolulu, and Lexington, Ky., whose bishop, John Stowe, went even further this week, making vaccination a condition for diocesan employment.

All have cited Vatican statements last year decreeing all three available vaccines to be “morally acceptable” despite their distant ties to abortion. Pope Francis, meanwhile, told an Italian television station earlier this year that he considered vaccination to be a moral obligation, citing a Catholic interest in advancing collective well-being.

And on Wednesday, the National Ad Council launched a public service campaign featuring the pontiff and several cardinals urging Catholics to get their shots.

And yet, bishops in states like Colorado, South Dakota, and North Carolina have circulated the NCBC’s exemption form letter among their flocks and said they would support any Catholics whose conscience told them to opt out.

“The rhetoric around this issue has gotten so inflamed, it feels that the church has become caught in the crosshairs,” Meaney said in an interview Wednesday. “I think it does reflect different realities in different parts of the country and perhaps different sensibilities of the bishops.”

Meaney acknowledged the controversy the NCBC’s stance has caused within the church and said some bishops have pushed the organization to revise it. He declined to specify which ones.

But he maintained he did not see the NCBC’s position as too far distant from those dioceses advising priests not to support objectors. Catholic teaching, he said, leaves ample room for individual discernment of conscience when it comes to medical decisions.

“I absolutely agree that there’s no strict religious obligation to object, but it’s not accurate to say there is no religious basis for exempting,” he said. “I agree in principle that a Catholic shouldn’t be required to provide a letter signed by a priest about what their Catholic belief is. Their Catholic belief doesn’t necessarily need to be validated by a church authority.”

As that heady theological debate continues, the number of Catholics actively citing their religion in seeking to opt out of vaccination remains unclear.

The Philadelphia Archdiocese acknowledged its priests have received inquiries from some parishioners, but declined requests to discuss the issue. Meaney said the NCBC has fielded more than 500 calls this year from Catholics struggling with the question.

A June study indicated U.S. Catholics were among the least-likely Christians in the United States to opt out — with only 6% of Hispanic Catholics and 8% white Catholics surveyed saying they would refuse vaccination. In contrast, 24% percent of white evangelical Christians and 13% of Black Protestants said they oppose COVID vaccination on religious grounds.

Earlier this year, La Salle University, a private Catholic campus in Philadelphia, implemented a vaccine mandate for its fall semester.

As of the deadline for filing exemptions, a spokesperson said, only 2% of students, faculty, and staff have sought to opt out.