Many Catholics have questions about whether the COVID-19 vaccines are morally acceptable under church teaching, especially the Johnson & Johnson vaccine which was developed using fetal stem cell lines.  It is an issue that both the Vatican and the U.S. Conference of Catholic Bishops (USCCB) have offered advice on, citing the common good underscored by the vaccine.  The USCCB advises:
“Given that the COVID-19 virus can involve serious health risks, it can be morally acceptable to receive a vaccine that uses abortion-derived cell lines if there are no other available vaccines comparable in safety and efficacy with no connection to abortion. If it is possible to choose among a number of equally safe and effective COVID-19 vaccines, the vaccine with the least connection to abortion-derived cell lines should be chosen.  If a vaccine with no connection to abortion-derived cell lines is not readily available, vaccines that used such cell lines only for testing would be preferable to those that use such cell lines for ongoing production. Such choices may not be possible, however, especially in the early stages of vaccine distribution. In that case, one may receive any of the clinically recommended vaccines in good conscience with the assurance that reception of such vaccines does not involve immoral cooperation in abortion.”