A precursor to vaccination (introduced by Edward Jenner in 1798), inoculation gave the patient a milder form of smallpox with better recovery rates than if the patient had acquired the disease naturally. The procedure provided lifetime immunity from a disease with a roughly 15–33% mortality rate. In June 1778, when the Continental -Army marched out of Valley Forge, they had completed "the first large-scale, state-sponsored immunization campaign in history." By continuing the inoculation program for new recruits, Washington better maintained military strength among the regular, Continental Army troops throughout the remainder of the war.