The World Fights Back – Development of the Polio Vaccine

Just over one hundred years ago, a man was born that would go on to develop a lifesaving vaccine that saved the lives of millions of children all over the world and although the disease is not eradicated completely, there are only around a thousand cases a year. The polio vaccine, developed by Jonas Salk, was the first ‘killed-vaccine’ where the virus is weakened and then injected and saved millions of lives around the world.

In developed countries these days (before the outbreak of Ebola), the most common disease we have to worry about is the flu but in the first half of the 20th century, polio was a worry among parents. In the United States in 1954 alone, there were over 35,000 cases of polio. The virus mainly affected children and epidemics were common every year. Children would have to spend their summer holidays indoor when the virus broke out as parents feared their children would end up in an iron lung (a large metal container that helped polio sufferers with breathing difficulties) or paralysed.  Approximately 2,000 children would die every year and another 20,000 would have some form of paralysis.

There are 3 main types of polio: sub-clinical, non-paralytic and paralytic. Sub-clinical polio is the most common (around 95% of cases) and the patient may not even get any symptoms. The virus does not enter the central system. Mild symptoms, if present, include headache, slight fever, vomiting or a sore throat. Non-paralytic is similar to sub-clinical as it is not very severe. It does however, enter the nervous system and produce minor symptoms but does not cause paralysis. These symptoms are normally similar to sub-clinical symptoms but can also include breathing difficulties or back and neck pain. Paralytic polio is the most serious of the three but also the rarest (approximately 1 in every 200 cases). The virus enters the central nervous system and causes paralysis in the patient. It can either cause spinal paralysis or bulbar paralysis which affects the brainstem. In some cases, patients can experience paralysis in both the spine and brainstem. Patients with paralytic polio tend to have a loss of reflexes and muscle spasms and it can lead to deformity of the limbs, most commonly hips, ankles and feet. There is no known cure for polio and all that doctors are able to do is to try and relieve the symptoms. This was a major reason for the push for a vaccine in the 1950’s.



The vaccine was developed by Jonas Salk at the University of Pittsburgh in 1952, but it would take another 3 years of testing before the vaccine was given to the world.  The vaccine was developed using monkey cells and killed with a chemical called formaldehyde.  The vaccine was one of the first to contain a weakened version of the virus. The development of the polio virus sparked the largest medical trial in history. Over 1.8 million children were involved in the trial which is known as a double blind placebo controlled trial. Around 1.8 million children in America took part with 440,000 children receiving the vaccine, 220,000 receiving a placebo and 1.2 million being observed as a control. The results were announced on the 12th April 1955 and the vaccine was declared safe. In the following years it was then given to millions of children in the United States and worldwide.

Nowadays, there are very few cases of polio around the globe, as it has been wiped out in all but around four countries. With the recent epidemic of Ebola, the fears people had in the 1950’s are coming back and there is a strong need for a vaccine to be developed that can once again save many lives.





Jonas Salk 1914-1995. (1998). Retrieved November 2014, from A Science Odyssey:

Klein, C. (2014, October 28). 8 Things You May Not Know About Jonas Salk and the Polio Vaccine. Retrieved 2014, from History:

Poliomyelitis (polio). (n.d.). Retrieved 2014, from World Health Organisation:

Steihm, J. (2014, October 31). When Science and Dr Jonas Salk conquered Polio. Miami Herald .


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