https://supreme.justia.com/cases/federal/us/197/11/
> Harlan ruled that the vaccination law did not violate the 14th Amendment because the police power of the state may be allowed to constrain individual liberties through reasonable regulations when required to protect public safety. He reasoned that individual liberty does not allow people to take actions regardless of the harm that they could cause to others. Harlan felt that the plaintiff had failed to show that the vaccination law was arbitrary or oppressive, or not reasonably required for the safety of the public. He noted the increasing presence of smallpox, which prevented the plaintiff from convincingly asserting that the rule had no real or substantial relation to protecting public health and safety. Although the plaintiff presented evidence that some doctors believed that the smallpox vaccine was not effective and could cause further diseases, Harlan pointed out that the opposite view represents the common medical belief and is followed by more reputable doctors.