When George Washington took command of the Continental Army in 1775, America was fighting a war on two fronts: one for independence from the British, and a second for survival against smallpox. Because Washington knew the ravages of the disease firsthand, he understood that the smallpox virus, then an invisible enemy, could cripple his army and end the war before it began.
That’s why Washington eventually made the bold decision to inoculate all American troops who had never been sickened with smallpox at a time when inoculation was a crude and often deadly process. His gamble paid off. The measure staved off smallpox long enough to win a years-long fight with the British. In the process, Washington pulled off the first massive, state-funded immunization campaign in American history.