1827: The “No child left unvaccinated” act becomes the law for Boston schools.

Smallpox was a deadly, disgusting disease, with the nasty habit of killing one-third of those who contracted the disease, and maiming those who were fortunate enough to survive it.

Boston’s declaration came just three decades after Edward Jenner discovered in 1796 that blister pus from those infected with the less-deadly cowpox could be used to immunize humans from smallpox.

Following Massachusetts’ lead, cities and states across the United States passed laws throughout the 19th century requiring citizens and...