"As a father of five, I have been confronted with the question of whether to vaccinate my children against rubella (“German measles”). As many now know, this vaccine is currently produced from a cell line that had its origin in abortion. Two other vaccines are similarly implicated in the tragedy of abortion: the hepatitis A and the new varicella (“chicken pox”) vaccines. As unfortunate as these facts are, an analysis of the problem, using traditional Catholic moral principles, does not seem to indicate that there is any obligation on the part of parents to avoid the use of these products. For my own part, therefore, I have not hesitated to have my children protected against these diseases. Nonetheless, there are many parents who have come to the opposite conclusion. They believe that it would be immoral to inoculate their children with these products. They hold that a vaccine with even the most remote connection to abortion is forbidden to them, and thus, they refuse immunization on the grounds of conscience. What is the status of this refusal? Can it be supported by Catholic teaching? We have a moral obligation to follow the light of conscience. Indeed, this duty is so fundamental that, even if one’s judgment is in error, conscience must still remain the standard of our conduct. To argue otherwise would be to say that we should do what we personally judge to be immoral."