On April 12, 1955, in a packed auditorium at the University of Michigan, a quiet researcher named Dr. Thomas Francis Jr. cleared his throat and read out three words America had been waiting years to hear: 'Safe, effective, and potent.' He was talking about the polio vaccine, developed by his former student Jonas Salk. Within minutes, the news flashed out across the country. Church bells started ringing.
Polio was the scariest disease that parents knew. Every summer, healthy children suddenly couldn't move their legs. Tens of thousands were paralyzed each year in the United States alone, and some had to live for months inside huge breathing machines called iron lungs. When Salk's vaccine was proven to work, the relief was nationwide. Department stores closed for a moment of silence. Drivers honked car horns. Strangers hugged on the street.
Within a few years, polio had nearly vanished from the United States. Today, thanks to ongoing global vaccination, polio cases worldwide have dropped by more than 99 percent. A single shot, announced on a spring afternoon in Michigan, started one of the biggest medical victories in human history.
