[2] In 1902, faced with an outbreak of smallpox, the Board of Health of the city of Cambridge, Massachusetts, adopted a regulation ordering the vaccination or revaccination of all its inhabitants.

[3] Although the efforts to eradicate smallpox were successful in Sweden, Jacobson's childhood vaccination had gone badly, leaving him with a "lifelong horror of the practice".

[2] Justice John Marshall Harlan delivered the decision for a 7–2 majority that the Massachusetts law did not violate the Fourteenth Amendment.

[2] However, the opinions offered by Jacobson were "more formidable by their number than by their inherent value" and "[w]hat everybody knows, ... [the] opposite theory accords with the common belief and is maintained by high medical authority.

[2] However, the statute in question was not "intended to be applied to such a case" and Jacobson "did not offer to prove that, by reason of his then condition, he was, in fact, not a fit subject of vaccination".

[11] The Supreme Court reaffirmed its decision in Jacobson in Zucht v. King (1922), which held that a school system could refuse admission to a student who failed to receive a required vaccination.

[12] Jacobson has been invoked in numerous other Supreme Court cases as an example of a baseline exercise of the police power, with cases relying on it including Buck v. Bell, 274 U.S. 200 (1927) (sterilization of those with intellectual disabilities),[13] Prince v. Massachusetts, 321 U.S. 158 (1944) (limitations on parents having children distribute pamphlets in the street), Cruzan v. Director, Missouri Department of Health, 497 U.S. 261 (1990) (allowing a state to require "clear and convincing evidence" of a patient's wishes for removal of life support), Vernonia School District 47J v. Acton, 515 U.S. 646 (1995) (allowing random drug testing of students), and Gonzales v. Carhart, 550 U.S. 124 (2007) (upholding the federal "partial birth abortion" ban).

[14][15] During the COVID-19 pandemic, the federal United States Court of Appeals for the Fifth Circuit relied on Jacobson when upholding a Texas regulation halting abortions by including it in its ban on non-essential medical services and surgeries, consistent with Justice Blackmun's citing of the case in Roe v.