University of Pittsburgh had begun immunization experiments in monkeys using dead polio virus. Soon, however, Salk began to test inoculations in paralyzed polio patients and by 1953 human trials among the general population were initiated. By the spring of the following year, the largest controlled field trials in medical history were underway, and by 1955 the vaccine developed by Salk and his researchers was declared effective. By 1962, Salk's vaccine had reduced the incidence of polio in the United States by 95 percent. The breakthroughs in immunology and vaccine development at Pitt by Salk and his team are considered one of the most
Salk Salk A salk () is a small military unit led by a senior soldier that is subordinate to an infantry squad. "Salk" is bigger than a lahingpaar ("fire and maneuver team") but smaller than a jagu ("squad"). It is also one of the smallest military formation among the Estonian Ground Force infantry units. It usually consists of three to five soldiers, and may be further subdivided into fire and maneuver teams. A "salk" is composed of two fire and maneuver teams of two soldiers each, as well as a fireteam leader ("salgapealik") who is usually a corporal ("kapral"). One single