Around 3 a.m. one November morning in 1721, a bomb crashed through the window of Cotton Mather’s Boston home. It had been hurled with such force that the fuse fell off, and it failed to detonate. Attached to the explosive was a warning note: “Cotton Mather, you dog, dam you: I’ll inoculate you with this; with a Pox to you.’’

The would-be bomber was not angry over politics, or love, or a business deal gone wrong, but rather over Mather’s attempts to save Boston residents from one of the deadliest threats of the era: smallpox. The same Puritan minister who played a role in fueling the execution of 14 women and six men during the Salem witch trials was now calling for the use of an experimental new way to prevent disease. Mather supported inoculation, a precursor to vaccination.

Nearly 300 years later, doctors are working to develop a vaccine for coronavirus — an infection far less lethal than smallpox — as people around the world clamor for treatment.