Benjamin Franklin in his autobiography said:

“In 1736 I lost one of my sons, a fine boy of four years old, by the smallpox taken in the common way. I long regretted bitterly and still regret that I had not given it to him by inoculation. This I mention for the sake of the parents who omit that operation, on the supposition that they should never forgive themselves if a child died under it; my example showing that the regret may be the same either way, and that, therefore, the safer should be chosen.”1

Good medical care requires making the right decisions—to test, treat or do nothing—in the face of uncertainty.2 Franklin came to believe he made the wrong decision to forgo smallpox inoculation for his son in 1736. We have enough information about Franklin’s decision, made over a quarter of a millennium ago, to evaluate his choice.

Benjamin Franklin was born in Boston in 1706. He worked as an apprentice to his brother James in a printing business in 1716 before moving to Philadelphia in 1723.34 During this era smallpox came periodically to these isolated commercial towns perhaps by way of an infected person on a merchant ship and swept through the town. Those who had been infected in the past and survived were immune. Most of the rest took smallpox “in the natural way” and lived or died from it. A few escaped the contagion all together. For about a decade afterwards, the town was immune to smallpox. A new generation of children were born and new people moved in. With time the unprotected proportion of the population grew. With each passing year without smallpox the risk of a new epidemic grew greater and the cycle would repeat itself. Boston had such epidemics in …