More than 300 years ago, during Boston’s 1721 smallpox epidemic, Onesimus, an African man enslaved by the Puritan minister Cotton Mather, shared knowledge of a centuries-old African practice known as variolation — a form of inoculation that could protect against smallpox.

That knowledge, passed from Onesimus to Mather and then to physician Zabdiel Boylston, was put into practice despite fierce public opposition. Boylston’s careful documentation showed that inoculation dramatically reduced deaths, providing some of the earliest evidence in North America that prevention could save lives.

Fifty years later, during the Revolutionary War, as smallpox threatened the Continental Army, General George Washington, the future president, made what was then an equally controversial decision: He ordered the inoculation of his troops. His decision helped preserve the army’s fighting strength at a pivotal moment in the war.

Read the full MassLive opinion piece.