The defining case in the field, according to Daniel A. Salmon, director of the Institute for Vaccine Safety at the Johns Hopkins Bloomberg School of Public Health, is the 1905 Supreme Court ruling in Jacobson v. Massachusetts.

The court upheld the authority of states to enforce compulsory vaccination on the grounds that, when danger loomed, an individual’s freedom could be subordinated to the common good.

The plaintiff, Henning Jacobson, was a Cambridge, Mass., pastor who had been vaccinated against smallpox as a child in Sweden and claimed it had caused him lifelong suffering.

He also argued that vaccination was an “invasion of his liberty” under the 14th Amendment. During a smallpox outbreak, he refused to let himself or his son be vaccinated and was fined $5.

Massachusetts was then one of 11 states with compulsory vaccination laws, but it did not allow vaccination by force. By a 7-to-2 vote, the court let the fine stand and said imprisonment could also have been imposed.

But Justice John Harlan wrote for the majority that individuals could not be forcibly vaccinated.

Yet vaccination by force was used in 1991 in Philadelphia, said Dr. Paul A. Offit, director of the Vaccine Education Center at the Children’s Hospital of Philadelphia.

A measles outbreak that year infected over 1,400 people and killed several children. It had begun in two fundamentalist churches that rejected modern medicine and practiced faith healing.