OMAHA, Nebraska — Four students are suing Creighton University over its requirement to get vaccinated against COVID-19 to remain enrolled, arguing that some of them “feel coerced” to violate their religious beliefs against abortion.

The lawsuit filed this week in Douglas County District Court also alleges that some of the four students have medical conditions that make vaccines not recommended for them.

The university in Omaha is affiliated with the Jesuit order of the Catholic Church. It mandated that all students get vaccinated in August, after the U.S. Food and Drug Administration granted full approval to a vaccine mandated by Pfizer, according to local news reports. The university had previously allowed medical exemptions to its vaccine requirements, but not religious ones.

The lawsuit says all four students have “religious objections” to COVID-19 vaccines because “the vaccines were developed and/or tested using abortion derived fetal cell lines.” Attorney Robert Sullivan said in a statement that a Catholic university should not place students in the position of having to violate the church’s teachings.

The Vatican declared in December that it is “morally acceptable” for Catholics to receive COVID-19 vaccines based on research that used cells derived from aborted fetuses, when “ethically irreproachable” vaccines aren’t available.

The university declined comment.