In the 2002 sci-fi noir film Minority Report, PreCrime, a specialized police agency, apprehends people who are forecast to commit crimes. No trial is necessary because the not-yet-committed crime is considered a vision of the future and thus a matter of fact. The film’s plot challenges viewers to consider the issue of free will vs. determinism, and consequently, the morality of punishing someone for a crime not yet committed. It serves as a useful metaphor for the argument against coercive vaccination.

Some argue that mandatory mass vaccination is an act of self-defense, and thus completely compatible with the principles underpinning a free society. Unless people are forcibly immunized, it’s argued, they will endanger the life and health of innocent bystanders. But such a position requires infallible precognition.

Not everyone who is vaccinated against a microbe develops immunity to that microbe. Conversely, some unvaccinated people never become infected. Some people have inborn “natural” immunity against certain viruses and other microorganisms. (Central Africans born with sickle cell trait provide a classic example of such inborn immunity: their sickle-shaped red blood cells are inhospitable to the mosquito-borne parasite that causes malaria. But there are innumerable less obvious examples.) Finally, some people are just lucky and never get exposed to a contagious microbe.

Just like not every pregnant woman who drinks alcohol or smokes tobacco passes on a malady or disability to her newborn baby, not every pregnant woman infected with a virus or other microbe passes on the infection to her fetus—nor are all such babies born with birth defects.

A free society demands adherence to the “non-aggression principle.” No person can initiate force against another, and can only use force in retaliation or in self-defense. Forcibly injecting substances—attenuated microbes or otherwise—into someone else’s body can not be justified as an act of self-defense, because there is no way to determine with certainty that the person will ever be responsible for disease transmission.

Aside from the obviously pernicious societal precedent set by the initiation of force against those who have not yet committed an act of aggression, there are also practical issues to consider.

How would coercive vaccination be enforced? What degree of invasion of personal information and privacy would be needed in order to make sure that everyone is vaccinated? How much liberty and autonomy would members of society have to surrender in order to make a system of coercive vaccination work? And what kind of liberty-infringing precedents would be established by enacting a mandatory vaccination program?

Then there is the matter of “herd immunity.”

The phenomenon of herd immunity allows many unvaccinated people to avoid disease because they free ride off the significant portion of the population that is immunized and doesn’t, therefore, spread a given disease. Economists point out that free riding is an unavoidable fact of life: people free ride when they purchase a new, improved, and cheaper product that was “pre-tested” on more affluent people who wanted to be the first to own it; people free ride when they use word-of-mouth reviews to buy goods or services, or to see a film; those who choose not to carry concealed weapons free ride a degree of personal safety off the small percentage of the public that carries concealed weapons. So long as a person being free-ridden is getting a desired value for an acceptable price, and is not being harmed by the free riding, it really shouldn’t matter to that person. Achieving a society without free riders is not only unnecessary, it is impossible.

So perhaps allowing a certain amount of free riders could mitigate the disruption to liberty caused by a mandatory vaccination program. But then, how many free riders should be allowed? And what criteria would be used to decide who gets to ride free?

As a medical doctor I am a strong advocate of vaccination against communicable and infectious diseases. I am irritated by the hysteria and pseudo-science behind much of the anti-vaccination literature and rhetoric. In my perfect world, everyone would agree with me and voluntarily get vaccinated against the gamut of nasty diseases for which we have vaccines. (In my perfect world, pregnant women wouldn’t smoke tobacco or drink alcohol until after delivery.)

But free societies are sometimes messy. 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.

A strong argument can be made that it is self-defense to quarantine people who are infected with a disease-producing organism and are objectively threatening the contamination of others. But in such a case, the use of force against the disease carrier is based upon evidence that the carrier is contagious and may infect others.

Any mass immunization program that uses compulsion rather than persuasion will, on balance, do more harm to the well being of a free people than any good it was intended to convey.