I work (in one of my personas) in healthcare. The hospital group I take most of my patients to addressed this by requiring people who wanted to claim a religious exemption also had to attest that they would and do not take [list of about 20 other fairly well known, fairly common medications] that also utilized stem cells in development.
It was not about "stem cells". Who told you that?
Several of the vaccines were manufactured using aborted fetal cell lines, such as HEK 293. Other Coronavirus vaccines were tested using these cell lines.
Some were morally unobjectionable, and our bishops assured pro-life people like myself that vaccination is "an act of mercy" towards our neighbors.
https://www.heritage.org/public-health/commentary/the-covid-...
Pro-life Christians have no objections to adult stem cells, but the cell lines in question here are not "stem cells" but directly cultures from murdered children... without knowledge or consent (see also: Henrietta Lacks.)