NEW YORK, July 8 — 1.8 million children. That is the figure that matters from the 1954 field trial of Jonas Salk’s inactivated polio vaccine. It remains the largest medical experiment in history, and it delivered results that reshaped American public health.
By the numbers: Polio cases in the United States had hit 35,000 in 1952 alone. The disease, which caused paralysis and death, swept through major epidemics in the 1940s and 1950s.
Salk, an American virologist born in 1914, developed the first effective vaccine using an inactivated virus. The bottom line came on April 12, 1955. That day, the trial results were announced: the vaccine was 80% to 90% effective.
It was licensed immediately. U.S. polio cases dropped from 29,000 in 1955 to 5,600 in 1957.
Salk became a national hero. But he did something that still stands as a landmark decision in medical economics: he declined to patent the vaccine. His reasoning, captured in a single question: “Could you patent the sun?” The science did not stop there.
Albert Sabin developed an oral polio vaccine in 1961, which became the primary tool for global eradication efforts. The Global Polio Eradication Initiative launched in 1988. By the numbers, that effort has reduced polio cases by over 99%.
In 2021, only 6 cases were reported worldwide. For context on the scale of the achievement: before Salk’s vaccine, polio was one of the most feared diseases in America.
The 1952 epidemic alone generated more cases than the total annual caseload in many subsequent decades. The vaccine’s rapid deployment — from trial to licensed product in a single day — remains a benchmark for regulatory efficiency. The figure that matters for the current global picture: 6 cases in 2021, down from hundreds of thousands annually before eradication efforts began.
The oral vaccine developed by Sabin proved more practical for mass immunization campaigns in developing countries, but it was Salk’s inactivated vaccine that proved the concept and broke the disease’s grip on the United States. Salk’s decision not to patent the vaccine had long-term implications for pharmaceutical economics.
It meant no single company held exclusive rights, allowing multiple manufacturers to produce the vaccine and drive down costs. That decision accelerated adoption and likely saved additional lives in the critical early years after the vaccine’s introduction. The field trial itself was a logistical achievement.
Organizing 1.8 million children for a controlled experiment required coordination across schools, health departments, and volunteer networks. By 1957, just two years after the vaccine’s introduction, the case count had fallen to 5,600. The Global Polio Eradication Initiative, now operating for nearly four decades, has brought the world to the threshold of eliminating a second human disease after smallpox.
The 99% reduction in cases represents one of the most successful international health campaigns ever mounted. The 6 cases reported in 2021 represent the lowest annual total in history.
The remaining transmission is concentrated in a handful of countries, primarily Afghanistan and Pakistan, where conflict and vaccine hesitancy have slowed the final push to zero. Salk died in 1995, having seen his vaccine transform American public health. He did not live to see the near-eradication of polio globally, but the framework he established — a safe, effective, non-patented vaccine tested in the largest clinical trial ever conducted — remains the foundation of that effort.
What to watch next: the final push to zero cases. The Global Polio Eradication Initiative continues surveillance and vaccination campaigns in the remaining endemic areas.
The oral vaccine developed by Sabin remains the primary tool, but Salk’s inactivated vaccine is still used in many countries as part of routine immunization schedules. The bottom line: a vaccine developed 70 years ago, tested on 1.8 million children, and never patented, has brought the world to within striking distance of eradicating a disease that once paralyzed tens of thousands of Americans every year. Consult your doctor for medical advice.
