We all know that George Washington was America’s first President. But perhaps it is lesser known, that as General, he had the entire Continental Army vaccinated against smallpox. This was the first mass inoculation in military history, and it was critical to ensuring America’s victory over the British.

Washington's first brush with smallpox came when he was 19 years old. For nearly a month, he battled a high fever, vomiting and pungent pustules. Smallpox is a deadly virus that has killed hundreds of millions worldwide. It is estimated that 300 million died of smallpox in the 20th century alone! Back in 1751, smallpox left Washington immune to the virus, but it also permanently pock-marked him for life. This would later contribute to his grizzled image as a leader. The scars also reminded him of the horrors and constant threat of smallpox. When Washington took command of the Army in 1775, a seven-year epidemic was just beginning that killed tens of thousands.

During the 1775-76 siege of Boston, the city was reeling from the epidemic. Washington took all possible measures to minimize its spread. He isolated his troops and only allowed those soldiers to attack Boston who had already survived smallpox (and were thus immune). His wary approach to smallpox helped keep his army healthy and functional. In contrast, the American forces who fought the British in Canada were devastated by smallpox, a chief reason for their defeat. Smallpox killed thousands in Canada and destroyed all hope of persuading Canadians to join the American Revolution. John Adams wrote in 1776, “The small-pox is ten times more terrible than Britons, Canadians, and Indians together.”

Back in Boston, Washington knew that simply evading smallpox was not enough. He then took the bold move of having the entire Army secretly inoculated. Modern vaccination methods didn’t exist, so doctors had to cut a patients arm and introduce the infected pus from a smallpox victim into the soldier's wound. Around 2% died from this process, but the survivors got lifelong immunity. By 1777, 40,000 soldiers were immunized and the results were stunning. The smallpox infection rate in the Army fell to only 1% and the Army developed into a powerful fighting force. A few years later the British surrendered and the United States of America was born. Were it not for George Washington’s experience with smallpox, history might have been written quite differently. Perhaps Americans would be driving on the left side of the road!

For another 200 years smallpox continued to ravage the world, until human beings finally achieved one of the greatest victories ever. In 1978, in the country that Washington helped create, smallpox was finally defeated as part of a multinational eradication program!