Vaccines and the Responsibility To Not Put Others at Risk

Ronald Bailey responds to Dr. Jeffrey Singer's "Vaccination and Free Choice"


This column is part of a debate over the proper view of vaccination in a free society. It began with a column by Reason's science correspondent, Ron Bailey, that argued that "people who refuse vaccination are asserting that they have a right to 'swing' their microbes at other people." Dr. Jeffrey Singer responded, writing, "To live in a free society, one must be willing to tolerate people who make bad decisions and bad choices." Bailey now continues the conversation.

I would like to thank Dr. Singer for a thoughtful response to my article. Before we get into the arguments for taking responsibility for your own microbes, let's review where Dr. Singer and I agree. First, we agree that vaccines are a safe and effective way to prevent and protect against communicable diseases. We agree that arguments to the contrary—e.g., assertions that vaccines cause autism and that thimerosal preservative is dangerous—are largely pseudoscientific nonsense. We agree that people who are known to be at a heightened risk from vaccines, such as people with impaired immune systems, should surely not be vaccinated. Interestingly, it is precisely immune-impaired people who would most benefit from the positive externality of widespread vaccination of other people. More on that topic below.

And I certainly agree with Dr. Singer when he states, "To live in a free society, one must be willing to tolerate people who make bad decisions and bad choices, as long as they don't directly infringe on the rights of others." But that is precisely what is at issue.

As Dr. Singer properly observes, one of the cornerstones of libertarian philosophy is the non-aggression principle. There is no canonical version, but at its heart is the idea that people are not permitted to initiate force against others except to defend themselves. That perspective is pretty well summarized by an Oliver Wendell Holmes quote I cited in my original article: "The right to swing my fist ends where the other man's nose begins." Just as an individual is responsible for where his fist is located vis a vis another's face, so too is he responsible for his microbes with regard another's health.

Some people object that aggression can only occur when someone intends to hit someone else; microbes just happen. Well, in medieval times, when diseases were blamed on demons and miasmas, people could not be expected to be responsible for their microbes. In the post-Pasteur era, people no longer have the excuse of ignorance. Being intentionally unvaccinated against highly contagious diseases is, to carry Holmes' analogy a bit further, like walking down a street randomly swinging your fists without warning. You may not hit an innocent bystander, but you've substantially increased the chances that you will.

One might usefully analogize the risk of disease to a crapshoot. A person's chance of being infected is, as Dr. Singer acknowledges, a matter of luck. But is it really OK for the unvaccinated to load the dice to increase the odds against other people? If so, by how much?

This raises the issue of utilitarianism. Some commenters on my original article dismissed the case of a vaccinated medical technician being hospitalized for measles caught from an intentionally unvaccinated kid, arguing that the possibility was too minor to worry about. Similarly, another observed that only 18 infants died from whooping cough out millions of babies last year. Never mind in each outbreak of whooping cough, about half of infected infants end up hospitalized. What could be more utilitarian than making those sorts of calculations? Those harmed by the irresponsibility of the unvaccinated in those cases are not being accorded the inherent equal dignity and rights that libertarians believe every individual possesses. The autonomy of the unvaccinated somehow trumps the autonomy of those they put at risk.

As central to libertarian thinking as the non-aggression principle is, there are other tenets that also inform a well-considered libertarian philosophy. One such is the harm principle, as outlined by John Stuart Mill in On Liberty. Mill argued that "the only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others." In his response, Dr. Singer limits the protection of others from infectious disease to those cases in which a known individual is currently spreading disease. In such a situation, Singer that a strong case can be made for legally detaining and isolating people in quarantine. I agree. But is the libertarian case for protecting people from the risk of infectious disease limited solely to quarantining those who are currently infected?

In his response, Dr. Singer uses the plot of the science-fiction movie, Minority Report, to compare the intentionally unvaccinated to those wrongfully convicted for crimes on the basis of allegedly infallible precognition. Dr. Singer is quite right when he states, "There is no way to determine with certainty that the [intentionally unvaccinated] person will ever be responsible for disease transmission." Since that is so, he suggests, people like me must be similarly endorsing a kind of "infallible precognition" with regard to which of the unvaccinated will cause disease in innocent bystanders. Not at all.

Dr. Singer correctly notes that vaccination fails to immunize some people; that some unvaccinated never come down with vaccine-preventable diseases; and that others are simply lucky enough never to be exposed. All true, but inapt. In Minority Report, the people convicted on the basis of precog "evidence" never knew or thought that they were a danger to others. No precognition is required to know that an individual's refusal to be vaccinated against highly contagious airborne illnesses puts others at risk of death, debilitation, hospitalization, and plain old misery.

Dr. Singer notes that mothers who smoke and drink alcohol increase the risk of harms to their fetuses. Quite true, but those actions are freely chosen and they do not put other people, including other women's fetuses, at risk of disease. Exposure to rubella does. In fact, researchers have reported that 100 percent of children whose mothers were infected with rubella before 11 weeks of gestation and 35 percent infected before 14 weeks were born with severe birth defects. As late as 1965, more than 2,000 kids were born with defects resulting from rubella infections. Now that an effective vaccine against German measles is available, who is responsible for those illnesses and defects? Surely not the mothers or their fetuses.

Dr. Singer clearly accepts the epidemiological reality of the positive externality of herd immunity. With regard to free riding on positive externalities, he further argues, "So long as the person being free-ridden is getting a desired value for an acceptable price, and is not being harmed by the freeriding, it really shouldn't matter to that person." If those of us who are successfully vaccinated obtain the benefits we are seeking, why should it matter to us that some refuse those benefits?

Here's why. Herd immunity is a positive externality that the vaccinated confer upon those who are too young to be vaccinated, who experience immunization failure, or who are immunocompromised. Immunocompromised people include people who have organ transplants, people who take certain drugs to ameliorate autoimmune diseases, medically fragile children, the elderly with senescent immune systems, and those infected with HIV. In America today, it is estimated that about 10 million people are immunocompromised. It is likely that the people responsible for those too young to be vaccinated and those who are immunocompromised would choose to take advantage of the protection offered by vaccination if they could, but they can't.

On the other hand, the intentionally unvaccinated are the only group that deliberately free-rides on the positive externality of herd immunity that the rest of us confer on them. And in exchange for this benefit, the unvaccinated inflict the negative externality of being possible vectors of disease, threatening millions who must depend through no fault of their own upon herd immunity. Vaccines are like fences. Fences keep your neighbor's livestock out of your pastures and yours out of his. Similarly, vaccines keep your neighbor's microbes out of your body and yours out of his.

Dr. Singer also recognizes that free riding by the intentionally unvaccinated could get out of hand when he asks, "How many free riders should be allowed?" One useful way to think about this question is to consider the population thresholds at which herd immunity breaks down. For most of the highly contagious airborne diseases for which vaccines are available those thresholds hover around having about 90 percent of people living in a community be vaccinated. Unfortunately, due to anti-vaccination propaganda those thresholds have been breached in numerous communities across the country. Outbreaks have resulted.

Dr. Singer worries that medical authoritarians would bend the arguments for vaccination to justify intrusions on liberty in the name of public health. Sadly, he is quite right. Already, nanny-state busybodies have ginned up "epidemics" of obesity and high blood pressure. Unlike people afflicted with contagious diseases, a fat person or a consumer of excessive amounts of salt cannot give someone else excess pounds or a heart attack. The arguments for vaccination apply only to situations in which innocent bystanders are at risk of being harmed by contagious microbes. Sticking to that limiting principle would prevent a fall down a slippery slope toward public-health totalitarianism.

Now let me directly address the issue of coercion. Dr. Singer—and many other readers—have been somewhat misled by the subhead on my article, "A pragmatic argument for coercive vaccination." I did not see that subtitle until after the article was published. My original article was supposed to make a more modest argument that vaccine refusal puts others at risk and that people should be responsible for their own microbes. My intent was to leave open the question of how to hold the intentionally unvaccinated liable for the damage they cause others, hoping to provoke readers to think about the issue and debate it among themselves. I stand behind what I wrote, but the subtitle has evidently somewhat diverted that discussion.

Education and the incentives of the market have encouraged lots of Americans to get themselves and their children vaccinated. Surely those avenues of persuasion have not been exhausted and should be used more. Perhaps schools and daycare centers could attract clients by advertising that they protect their charges by refusing to admit unvaccinated students. Or social pressure might be exercised by parents who insist on assurances from other parents that their children are vaccinated before agreeing to playdates. But it would be naïve not to note that state requirements that public school children be vaccinated against many highly contagious diseases have more than merely nudged most parents into getting their children vaccinated.

In the case of vaccination, the non-aggression principle, the harm principle, and proper respect for the autonomy of others combine to point to the libertarian conclusion that the intentionally unvaccinated do not have a right to "swing" their microbes at other people.