The case of Jacobson v. Massachusetts centered around the Massachusetts law that required smallpox vaccinations in order to combat outbreaks of the disease. In 1902, Henning Jacobson, a resident of Cambridge, Massachusetts, refused vaccination for his son, asserting that the vaccine posed health risks and violated his rights to personal liberty. His refusal led to a fine imposed by the city, which Jacobson contested in court. Initially dismissed by lower courts, the case was escalated to the U.S. Supreme Court, which ultimately had to weigh the tension between individual freedoms and public health imperatives.

On February 20, 1905, the Supreme Court ruled in favor of Massachusetts, declaring by a 7-2 majority that the state had a legitimate authority to mandate vaccinations to protect the health of its citizens. Justice John Marshall Harlan, who wrote the majority opinion, stated that individual liberties could be limited when necessary for the common good, thus establishing a significant precedent. The court acknowledged the historical context of smallpox's devastation, recognizing public health as a key component of government responsibility.

This ruling set a judicial precedent for future public health policies, influencing how states could regulate health measures. It was a foundational case in the ongoing debate surrounding personal freedoms versus collective safety, which would reverberate through legal and medical discussions in the U.S. for years to come, particularly in matters related to vaccination and health mandates.