Source: The Washington Post - Link
There is a long-standing debate in the Catholic Church over accepting vaccines and treatments that use fetal tissue, centering on HEK293 cells, which are cloned from an aborted fetus from the early 1970s, according to Religion News Service. The cells used now, such as those used in the Johnson & Johnson vaccine, are not from the original fetal tissue.
All the vaccines are “tainted” in some way. The pope has weighed in on this. It’s the US bishops that are balking.