Table of Contents • I. Poliomyelitis, Treatment, and Prevention Prior to 1955 • A. Poliovirus and Poliomyelitis • B. The Endemic Phase (Antiquity to ~1880) • C. Epidemic Emergence (1880-1920) • D. The Epidemic Phase (1920-1955) • E. The Path to a Vaccine • II. The Arrival of the Salk Polio Vaccine: Documents, April-July 1955 • III. Postscript - Polio Prevention after Jonas Salk • IV. Bibliography and Resources • V. Student Assignments • VI. Catalogue of Sources

Section I: Poliomyelitis, Treatment, and Prevention Prior to 1955

E. The Path to a Vaccine

Throughout the 1930s and 40s, the primary focus of the National Foundation's research support was toward the development of a vaccine against polio. President Roosevelt died in 1945, at a time when annual polio rates were increasing once again.

By the late 1940s, researchers around the country were supported by the National Foundation, studying the virus and testing strategies that might lead to a safe and effective vaccine against polio. Among these researchers were Drs. John Enders, Frederick Robbins and Thomas Weller at Harvard University, who would share the Nobel Prize in Medicine for their work growing polio in culture. Also studying the virus were Dr. Albert Sabin at the University of Cincinnati and Dr. Jonas Salk at the University of Pittsburgh.

Two strategies emerged for a potential vaccine that would provide protection against polio. The first, pursued by Salk, involved inactivating (killing) the virus through exposure to formaldehyde. The alternative, investigated by Sabin, was to weaken (attenuate) the live poliovirus so that it could no longer cause symptoms of the disease.

With major funding from the National Foundation, Salk's strategy advanced most quickly. Following another increase in annual polio rates and a major epidemic in the United States in 1952 (Figures 2 and 5, Document A), the vaccine candidate developed by Salk was ready for clinical testing. Following small-scale testing in and around Pittsburgh (including Salk giving the still experimental vaccine to himself and his children), a massive field test of the vaccine began in 1954. Two million children age 6 to 9, dubbed "Polio Pioneers," participated in a double-blind trial designed to assess the benefit of the Salk vaccine versus a placebo.

The results of the trial would be examined and announced by Dr. Thomas Francis of the Vaccine Evaluation Center at the University of Michigan. At a press conference on 12 April 1955 (the 10th anniversary of FDR's death), Francis announced to the assembled press, the nation, and the world that the Salk polio vaccine was 60-90% effective at preventing polio, a dramatic success that immediately transformed Jonas Salk into a national hero. A portion of his remarks at the announcement is included in Video Clip N.

Video Clip N - Excerpt of Remarks from Dr. Jonas Salk at Announcement of Trial Results, 12 April 1955 (You must have RealPlayer installed to play this video.)

Immediately following the formal announcement, Francis, Salk, and O'Connor participated in a press conference, a portion of which appears in Video Clip O.

Video Clip O - Statement from Dr. Thomas Francis at Press Conference Following Announcement of Trial Results, 12 April 1955 (You must have RealPlayer installed to play this video.)

The announcement of the field trial results was eagerly anticipated nationwide, but was of particular interest to the medical community. Later that day, a special closed-circuit broadcast (a technological marvel in 1955) was organized to share with physicians the implications of the trial results. Footage of the moments immediately before this broadcast appears in Video Clip P.

Video Clip P - Portion of Nationwide Broadcast for Physicians to Explain Trial Results, 12 April 1955 (You must have RealPlayer installed to play this video.)

The vaccine was licensed by the federal government that same day. With the annual polio season approaching and a safe and effective vaccine now available, efforts focused on manufacturing, distributing, and administering the vaccine as quickly as possible.

Continue to The Arrival of the Salk Polio Vaccine: Documents, April-July 1955