A suburban New York county has banned all unvaccinated minors from public places in hopes of staving off a recent measles outbreak in the area. This comes on the heels of a Northern Kentucky Health Department decision to ban unvaccinated students from school after a chickenpox outbreak there. Parents cite various reasons for not vaccinating their children, including religious ones because of a tie that some vaccines have to abortion. With the “anti-vaxx” movement on the rise, it is a good time to examine vaccines from a Catholic moral viewpoint.

The ties that link vaccines with abortion are not the only, nor possibly the most important, moral aspect of the question. Living as we do in a post-vaccine world, we do not realize just how deadly many of the diseases we are inoculated against really were. According to the CDC, “in 1920, 469,924 measles cases were reported, and 7,575 patients died; 147,991 diphtheria cases were reported, and 13,170 patients died. In 1922, 107,473 pertussis cases were reported, and 5,099 patients died.”  These pale in comparison with polio, which in each of the five years prior to the vaccine’s introduction saw  “an average of 16,316 paralytic polio cases and 1,879 deaths from polio.” These statistics are important, not because they enable us to perform some moral calculus but because they show that vaccines are not merely a personal decision. They have profound social implications.

Many people with various immune deficiencies would do well to be inoculated against these diseases but can’t be. These “weakest among us” then depend on other people who are physically healthy enough to be inoculated in order to maintain “herd immunity.” When total immunity within a population is impossible, then the best that a society can hope for is to prevent any outbreaks of the disease. As long as 90% of a population is immune to a disease, the prevalence will remain rather low. Such “herd immunity” is the benchmark public health officials strive towards. As the herd-immunity percentage decreases, the likelihood of an outbreak increases. The weakest in society are the most prone to suffer when an outbreak occurs.

Hiding behind the name “public health” is the Catholic principle of the common good, the social conditions that lead to human thriving. The good of health flows over each member of a society, but especially those who are most vulnerable. When a healthy member of society receives a vaccination, he may forgo some personal good like avoiding the fear of needles or other temporary side effects, but in doing so he contributes to (and also shares in) the common good.

Because we have an obligation to contribute to the common good, we also must say that we have an obligation to be inoculated. (This assumes it does not constitute an excessive burden or a serious risk. Also, a special case can be made against the vaccine for HPV, a sexually transmitted disease. Because of the manner of transmission, this disease can be avoided by living a chaste life. There would be no obligation, then, to be immunized against HPV, even if one might choose to do so later on.

While it is clear that we have a moral obligation to receive immunizations, there is still the so-called “religious” objection. The chickenpox, the rubella, and the Hepatitis-A vaccines have a historic link to fetal tissue harvested from aborted children in the 1960s. Despite the fact that we have a moral obligation to contribute to the common good, this link to abortion, for many, is a deal-breaker. Some explanation may help here: Although the cell line may have been derived from an aborted human person, the actual cells that one receives in the immunization does not contain any cells from the original abortion. These cells have been grown independent of those children who were killed.

More important, one must understand what it means to cooperate with evil. When the Pontifical Academy for Life took up this question in 2005, they framed it from within the context of the Principle of Cooperation. This moral principle recognizes that a number of people may directly and indirectly participate in bringing about an evil action. Some contribute willingly (formal cooperation) and some only contribute materially. Some play a vital role in bringing about the result (immediate material cooperation) and some only accidentally and nonessentially (mediate material cooperation). For those who receive immunizations, the cooperation is mediate material cooperation at best. Provided they voice an objection and choose an alternative when possible, they have committed no moral wrong.

St. Thomas Aquinas says that, provided we do not participate in another person’s sin, we may follow the divine example of bringing good out of another’s evil (c.f. ST II-II, q.78, art.2). Assuming we do nothing to create a “market” or demand for more fetal cells, then this seems to be a good example of bringing some good out of a heinous crime. Those who are able should be immunized.