Polio

Polio History
Polio was not discovered to be contagious until 1905 by Swedish physician Ivar Wickham. In 1908, Karl Lansdteiner, MD, and Erwin Popper, MD, identified and isolated the polio virus. The idea of a vaccine against polio was first introduced in 1910 as a result of research by Simon Flexner, MD. In 1935 two teams tested a polio vaccine but neither were successful and both teams infected and killed some test subjects (the scientists, chimpanzees, human adults, and children). In 1951, Jonas Salk, MD, and his team developed a method to cultivate polio virus in monkey kidney tissue in order to be able to produce large amounts of the vaccine. On Apr. 12, 1955 the results of the Salk vaccine trials showed the vaccine was 80-90% effective and the US government licensed the IPV (inactivated polio vaccine) vaccine the same day. The vaccination program was suspended on May 8, 1955 to investigate paralysis resulting from the vaccine injection; changes to the production method were made and vaccination resumed on May 27, 1955. On Aug. 24, 1960, a polio vaccine (OPV; oral polio vaccine) created by Albert Sabin, MD, was licensed for use in the US and recommended by US Surgeon General Leroy E. Burney, MD. In 1968 US use of Salk’s IPV vaccine was phased out. Polio was declared eradicated in the Americas on Sep. 29, 1994 by the Pan American Health Organization. An improved version of Jonas Salk’s IPV vaccine was phased in again in 1997, because OPV had an increased risk of infecting children with the virus in the first dose. In 2000 the transition to all-IPV vaccine schedule was complete.

Below are three graphs. The first shows the number of polio cases in the United States, adults and children, from 1937 to 2013. The second graph shows the number of deaths caused by the polio virus in adults and children from 1950 to 2013. And the third graph shows the polio vaccination rates among children aged 19 to 36 months in the United States from 1980 to 2014.

As of Aug. 18, 2014, the CDC recommends that children receive the first dose of the polio (IPV) vaccination at 2 months of age.

Microscopic view of the polio virus
Source: Sanofi Pasteur, “Polio Virus (picornavirus): Virus Responsible for Poliomyelitus (picornavirus),” www.flickr.com, Aug. 7, 2013