"It is important to note that the use of these vaccines, generated from fetal tissue of elective abortions, can only occur on a temporary basis, as it represents a “very remote mediate material cooperation” (Pontifical Academy for Life 2006, 547) with the original illicit act of abortion. The distinctions between the different forms of cooperation were established by St. Alphonsus Liguori and can be categorized by the proximity of actions to the original illicit act. An example using vaccines generated from fetal tissue of an elective abortion follows: Principal agent: The mother who elects to terminate her pregnancy. Formal cooperator: The abortionist who agrees with the actions of the principal agent and supports her by performing the abortion. Immediate material cooperator: A nurse who does not agree with the actions of the principal agent but supports the abortionist in performance of the abortion. Mediate material cooperators: The nurse who does not agree with the actions of the principal agent but prepares her for the abortion and monitors her recovery post-abortion. Remote mediate material cooperators: The technicians at the abortion clinic that process and package fetal tissue for future use in scientific research. The scientists who arrange to receive aborted fetal tissue from the clinic for their research. Very remote mediate material cooperators: Individuals utilizing a product, for example a vaccine that was generated utilizing aborted fetal tissue. Even the distant cooperation represented by these vaccines needs to be avoided as it is: moral coercion of the conscience of the parents, who are forced to choose to act against their conscience or otherwise, to put the health of their children and the population as a whole at risk. ...[Therefore,] doctors and fathers of families have a duty to take recourse to alternative vaccines (if they exist), putting pressure on the political authorities and health systems so that other vaccines without moral problems become available. (Pontifical Academy for Life 2006, 549, 547–8)"