Mandatory Vaccination: Harm to Self or Harm to Others?

Mandatory vaccination often ends up on lists of "paternalistic" measures. But on closer inspection it is rather a pure case of the Millian harm principle — only here the harm is done to others.

Paternalism or Protection of Third Parties

The key distinction: paternalism protects a person from himself, whereas the harm principle protects others from him. Vaccination creates herd immunity and protects those who cannot be vaccinated. Its mandatory character is therefore justified by the protection of third parties, not by the good of the vaccinated person himself (SEP: Paternalism).

The Mathematics of the Threshold

The herd-immunity threshold depends on infectiousness and is calculated as 1 − 1/R₀. For measles the basic reproduction number is estimated at 12–18 (The Lancet Infectious Diseases), which requires about 95% coverage with two doses of vaccine to interrupt transmission (WHO: measles).

The Scale of the Problem

The stakes are high: according to the WHO, in 2024 only about 84% of children received the first dose of measles vaccine, and some 11 million measles cases and about 95,000 deaths were recorded worldwide — chiefly among unvaccinated children under 5 (WHO).

Jacobson v. Massachusetts (1905)

The legal framework was set by an American precedent: in Jacobson v. Massachusetts (197 U.S. 11, 1905) the U.S. Supreme Court upheld a state's right to impose mandatory smallpox vaccination, invoking the "police power" and the community's right to defend itself against an epidemic (Justia). The Court stated outright that individual liberty is not absolute and is subject to measures necessary for the common good.

School Mandates

The main institution for controlling coverage is the school: in the United States, vaccination requirements for enrolment are in force in every state, differing in their grounds for exemption (medical, religious, philosophical). It is precisely around these exemptions that the principal contemporary dispute turns.

Where the Boundary of Coercion Lies

Vaccination shows that the label "paternalism" must be applied carefully. Where an intervention protects others, the harm principle is at work and the bar of justification is lower. Paternalism in the strict sense would begin if a vaccine were imposed for the person's own good in the absence of any risk to those around him — and that is already quite a different, more contentious case.