California has many attractions that international travelers and local residents alike can visit. Since we are residents of southern California, my family is lucky to be able to frequent the San Diego Zoo, San Diego Safari Park, the beaches of Coronado and La Jolla Shores, and amusement parks like LEGOLAND and Disneyland. For the past year we have been annual passport holders for Disneyland and California Adventure Park, and I can’t tell you how much fun it is to enjoy a day away from committee meetings and grading to instead fly through the London sky on Peter Pan’s ride, or hear your 2-year old sing along to “It’s A Small World” or see your 4-year old daughter’s delight at spotting Elsa and Anna in the holiday parade. For the moment, I will bracket my critique of princess culture and the consumerism of family amusement parks—those are important, to be sure; but Disneyland provides an escape into a world of imagination and creativity in a kid-friendly environment. Given my interest in local family attractions, I’ve been following the news of the measles outbreak very closely. The Centers for Disease Control and Prevention reports that 102 people in the United States have been diagnosed with measles so far in 2015, in 14 states: Arizona, California, Colorado, Illinois, Minnesota, Michigan, Nebraska, New York, Oregon, Pennsylvania, South Dakota, Texas, Utah, and Washington. 67 of those cases are the result of airborne transmission at the Disneyland theme parks from December 17-20, 2014. My family attended California Adventure on December 18th. Thankfully, we were not infected. We are all vaccinated, so our risk of contracting measles was low. But for unvaccinated people, or those with weakened immune systems, measles is not exactly the souvenir you want to bring home from your vacation.

Dr. Anne Schuchat, the assistant surgeon general, U.S. Public Health Service and director of the CDC’s National Center for Immunization and Respiratory Diseases, explained in a press conference:

State and local health departments are investigating the large multistate outbreak related to the theme parks and the initial cases reported visiting the resorts between December 17th and December 20th, 2014. So far we know of 67 confirmed cases of measles linked to the outbreak and they have occurred in California and six other states. We don’t know exactly how this outbreak started but we do think it’s likely a person who was infected with measles overseas and who visited the Disney parks in December when they were still infectious. This reminds us that measles exposures can happen in this country in many settings and insuring age appropriate vaccinations for all U.S. residents is very important. Maintaining high vaccination coverage is very important and it’s the best protection we have against disease outbreaks.

What Dr. Schuchat is referring to here is called “herd immunity,” and as I will argue, Catholics should find this argument persuasive given the theological anthropology—or way of understanding the human person—found in Catholic teachings.

So what is herd immunity? Since good theological ethics must engage the best of the scientific knowledge, let’s see what we can learn from scientists, epidemiologists, and doctors. My primary resources here are the Centers for Disease Control and Prevention and the College of Physicians of Philadelphia award-winning educational resource: According to the CPP:

When a large percentage of the population is vaccinated, the spread of disease is limited. This indirectly protects unimmunized individuals, including those who can’t be vaccinated and those for whom vaccination was not successful. This is the principle of herd immunity.

In diseases spread from person to person, it is more difficult to maintain a chain of infection when much of the population is vaccinated. As the number of those vaccinated increases, the protective effect of herd immunity increases. For some diseases, herd immunity may begin to be inducted with as little as 40% of the population vaccinated. More commonly, and depending on the contagiousness of the disease, vaccination rates may need to be as high as 80-95%. This percentage is called the herd immunity threshold.

When only a small percentage of the population is vaccinated, the risk of a disease outbreak is greater than if many are vaccinated. The unvaccinated members of the population are not indirectly protected, and each community member has a high risk of becoming infected.

In other words, if JoAnna Wahlund of Catholic Stand makes the irresponsible decision of not vaccinating her children because of her claim of conscience, and her children do not become infected with measles, it will be because her family benefits from the herd immunity in her community. Her child would be called a “freeloader”—that is, unless enough people follow Catholic Stand’s lead to the point that herd immunity breaks down (in that case, her child could become an agent of transmission, with potentially death-dealing consequences for someone else’s child).

Let’s be clear. Public health and Catholic social teaching share a common concern for social justice. When we are talking about public health we are no longer simply talking about individual decisions. We are talking about the health of populations. We take the perspective of medicine (patient care at “three feet,” or face to face) and bring it up to the scale of public health (the aerial view of 30,000 feet). And the consequences of individual decisions can be severe indeed, especially for those made vulnerable by infancy, pregnancy, or immune suppression.

Dr. Schachut puts it this way:

I do want to remind you that unvaccinated people put themselves and others at risk for measles for complications. Young babies cannot get this vaccine but they are very vulnerable to measles and complications. Pregnant women and people with compromising conditions like leukemia can’t get the vaccination and they are depending on others to have been vaccinated. We hope pregnant women have been vaccinated as children but we are learning of some who have not been vaccinated so they have to be protected through other means. This is not just to protect ourselves and our families but to protect the vulnerable in our community.

And this is where Catholics should recognize that the wisdom of our theo-ethical tradition aligns with public health. Protection of the vulnerable is a key principle of Catholic social thought. While the public health community employs the term “herd immunity,” the basis for such a claim is that human beings are social creatures. And this claim is found all throughout the social encyclicals, as popes in the modern era have emphasized a theological anthropology (or theological vision of the human person) that is social by nature. In Quadragesimo Anno (1931), Pope Piux XI discussed the “social character of human beings” (sometimes translated as the “social nature of men,” no. 42). In 1961, Pope John XXIII recognized: “One of the principle characteristics of our time is the multiplication of social relationships, that is a daily more complex interdependence of citizens, introducing into their lives and activities many and varied forms of associations” (Mater et Magistra, no. 59).

While I’m sure the pope did not have the Disneyland theme park in mind, the current measles outbreak is a result of just this kind of “varied forms of association” given the complex nature of our world today. For the researchers at the front lines of this epidemic who are currently engaged in shoe leather epidemiology, following all possible leads and tracking down the schedules and social networks of infected and affected persons, the complexity of our social lives and daily interactions is part of the fact of contemporary life.

For those readers who’ve been snowed in for the past three days, consider how your daily interactions have been restricted in comparison to a normal work day. As I calculate the number of people with whom I’ve interacted today, including family members, teachers and children at my kids’ school, my students and colleagues, and the people I came into contact with during my post-work errands, I estimate that I’ve interacted with 128 people in the past twelve hours.

And for measles, it doesn’t take much. Measles is a highly infectious, airborne disease that typically begins with fever, cough, runny nose and red eyes, and within a few days a red rash appears, usually first on the face and then spreading downward to the rest of the body.

Again, Dr. Schuchat reminds us:

People don’t always know they are infectious because you can spread the disease before the rash is evident. Measles is so contagious that if one person has it, 90% of the people close to the person who aren’t immune will also be infected. You can catch it just by being in the same room as a person with measles even if that person left the room because the virus can hang around for a couple of hours.

In other words, even if you do not intend to harm another person by failing to vaccinate yourself or your children (when medically indicated), the potential harm you might cause is very real. Given that, for U.S. residents, these vaccines are widely available, affordable, safe, and effective, there are no good reasons for choosing not to vaccinate your children.

A Catholic common-good approach to the prevention of disease is grounded in a vision of a loving God who desires human flourishing. As Gaudium et Spes reminds us, humans were created by God not for life in isolation but for the formation of social unity (no 32). According to David Hollenbach, “the communitarian character of human existence means that the good of each person is bound up with the good of the community. Thus the obligations of justice and love will only be fulfilled when each person contributes to the common good in accord with his or her abilities and in light of the needs of others.” (David Hollenbach, “Principle of the Common Good,” in The New Dictionary of Catholic Social Thought, pg. 192).

Too many children die unnecessarily of preventable childhood diseases. You can read about the World Health Organization’s Global Vaccine Action Plan here. And about the vaccine-preventable diseases at the CDC website here. Disease eradication and good global health investment are an essential part of “integral human development” as promoted by the United States Conference of Catholic Bishops and their global relief work through Catholic Relief Services.

The Integral Human Development framework, championed by Catholic Relief Services, provides an example of this social vision:

Integral Human Development (IHD) is a central component of the CRS agency strategy and the work CRS does with its partners. The concept, founded in Catholic social teaching, affirms that human development cannot be reduced or separated into component parts.  Rather, personal wellbeing can only be achieved in the context of just and peaceful relationships and a thriving environment.  It is the sustained growth that everyone has the right to enjoy. IHD promotes the good of every person and the whole person; it is cultural, economic, political, social and spiritual. 

Our African brothers and sisters remind us of this truth in the claim, “I am because we are.” Personal fulfillment is empty when taken out of the context of a rich communal life. (See also Populorum Progressio, no. 21, and Gaudium et spes, nos 24-25). According to Catholic theologian Charles Curran, “Catholic social teaching recognizes that the whole of the Catholic tradition testifies to the social nature of human beings. Through creation we are all brothers and sisters who have the same God as our Creator.” (Catholic Social Teaching 1891-Present: A Historical, Theological, and Ethical Analysis, 133.) Pope John Paul II repeatedly focused on the recognition of human interdependence and the virtue of solidarity, as he discussed in Solicitudo Rei Socialis, nos. 38-39:

On the path toward the desired conversion, toward the overcoming of the moral obstacles to development, it is already possible to point to the positive and moral value of the growing awareness of interdependence among individuals and nations. The fact that men and women in various parts of the world feel personally affected by the injustices and violations of human rights committed in distant countries, countries which perhaps they will never visit, is a further sign of a reality transformed into awareness, thus acquiring a moral connotation.

It is above all a question of interdependence, sensed as a system determining relationships in the contemporary world, in its economic, cultural, political and religious elements, and accepted as a moral category. When interdependence becomes recognized in this way, the correlative response as a moral and social attitude, as a “virtue,” is solidarity. This then is not a feeling of vague compassion or shallow distress at the misfortunes of so many people, both near and far. On the contrary, it is a firm and persevering determination to commit oneself to the common good; that is to say to the good of all and of each individual, because we are all really responsible for all…. Those who are more influential, because they have a greater share of goods and common services, should feel responsible for the weaker.

Catholic social teachings do no promote blind collectivism; rather, they emphasize the wisdom of understanding connectedness and mutual relationships of interdependence. Curran finds that the harshest critics of Catholic social teaching are those who stress an individualistic and libertarian ethic  “that does not give enough importance to the social nature of the human person” (Curran, 136). But even Rand Paul has come to his senses (at least on this issue) and now explicitly says that he supports vaccinations. Others respond with satire. The Onion is always the best.

This is a time to ask ourselves how committed we are to the common good. Vaccinations and investment in health care infrastructure are important steps in creating healthy populations. There is considerable overlap in the wisdom of both Catholic social teachings and mainstream research in public health and epidemiology.

If you would like to help Catholic Relief Services provide vaccinations to children worldwide, donate here.