Whichever direction the experiment went, there was a simple way to monitor the progress. Added to the test-tube mixtures was a red dye that was sensitive to acidity. If the cells had been killed by the virus, the fluid would stay red, signaling that no antibodies had been produced. If live, healthy cells were present—protected by vaccine-induced antibodies—the dye would turn yellow, signaling success.
One morning in mid-September, Elsie Ward came to the lab earlier than usual. Just the day before, Salk had determined the time was at last right to mix the blood serum from the Watson children with the poliovirus. It could take at least 24 hours for the experiment to play out and the tubes to change—or not change—their telltale color.
Opening the main door on the first floor, Ward flipped on the lights and made her way down the checkerboard-tiled hallway. Entering her small room, she threw on the light and cast her eyes to her tidy lab station with its big rack of 128 test tubes. The first thing she noticed was an unmistakable scream of yellow flashing back to her from inside the tubes.
As a rule, Ward was not one to exclaim much. “Oh, my!” was all she would typically say—and “Oh, my!” was what she said this morning.
Other members of the team trickled in, saw what she had discovered and whooped exuberantly. Finally, Salk himself appeared. Most mornings, he did not begin his workday until he performed a little ritual, stopping in his office to remove his sport jacket and slip on his white lab coat. Today, however, he was out of uniform, clad in his jacket with the lab coat nowhere in sight. He had apparently beaten a path for Elsie Ward’s lab.
“How do they look?” he asked.
Ward pointed to the rack. “It worked!” she said.
Salk made his way through the group, smiling broadly. On more than one occasion he’d told his staff that what they were looking for in their polio studies was a yes from nature—some hard confirmation that the path they were pursuing was the correct one. What he saw at Elsie Ward’s workstation was that yes.
“Good for you,” he said, examining the test tubes more closely. “Well done.” Then he turned to the rest of the group. “OK,” he said. “Now let’s make sure we can do it again.”
Salk and his team were indeed able to reproduce their findings. So consistently did they do so that in April 1954, the NFIP finally gave its approval for a nationwide field trial of 1.8 million children in 44 states. The study was conducted that spring and summer, the results collected in the fall. Throughout the long winter of 1954 and 1955, a commission headed by Thomas Francis worked to interpret what the numbers meant. On April 12, 1955—ten years to the day after the death of Franklin Roosevelt—Francis was set to issue his report in the University of Michigan’s Rackham Lecture Hall.