On April 26, 1954, the Salk polio vaccine field trials, involving 1.8
million children, began at the Franklin Sherman Elementary School
in McLean, Virginia. Children in the United States, Canada and
Finland participated in the trials, which used for the first time the
now-standard double-blind method, whereby neither the patient
nor attending doctor knew if the inoculation was the vaccine or a placebo.

One year later, on April 12, 1955, researchers announced the vaccine
was safe and effective and it quickly became a standard part of childhood immunizations in America.

The United States detonates the world’s first thermonuclear weapon, the
hydrogen bomb, on Eniwetok atoll in the Pacific. The test gave the United
States a short-lived advantage in the nuclear arms race with the Soviet
Union. 

Following the successful Soviet detonation of an atomic device in 1949,
the United States accelerated its program to develop the next stage in
atomic weaponry, a thermonuclear bomb. Popularly known as the
hydrogen bomb, this new weapon was approximately 1,000 times more
powerful than conventional nuclear devices. Opponents of development
of the hydrogen bomb included J. Robert Oppenheimer, one of the fathers
of the atomic bomb. He and others argued that little would be accomplished
except the speeding up of the arms race, since it was assumed that the
Soviets would quickly follow suit.The opponents were correct in their
assumptions. The Soviet Union exploded a thermonuclear device the
following year and by the late 1970s, seven nations had constructed
hydrogen bombs. The nuclear arms race had taken a step forward.