Polio is an infectious disease, caused by a virus, that attacks the muscles, most commonly in the legs.

In 1952 Jonas Salk, working at the University of Pittsburgh, developed a vaccine. After tests it was announced to the world on April 12th 1955 by Dr Thomas Francis.

Sanitation improves, Polio increases

Most diseases decrease as sanitation gets better, but Polio was an exception. Noted as far back as Egyptian times, many communities had become fairly immune to Polio. Polio does not generally attack babies and infants and so many children had already become exposed and immune to polio by the time they reached 5 years old.

Developments in sewage treatment in the 19th and 20th century meant less infants met Polio at a young age. This led to a sudden increase in Polio at the beginning of the 20th century.

By 1952 the US alone had 58000 cases, resulting in over 3000 deaths a year and over 21000 people with some sort of paralysis.

Salk’s Vaccine

On April 12th Jonas Salk announced he had developed a vaccine for polio. This vaccine was created by giving infants an ‘inactivated’ (dead) polio injection, thus making them immune.

Dr Thomas Francis began the largest medical experiment in history, testing 1.8million children across 44 states of the US.

From 35 000 cases in the US in 1953, the number fell to 161 in 1961.

Salk made a famous quote in an interview about his vaccine: when asked why he had not patented to earn money, he replied ‘Would you patent the sun?’


In 1957 Albert Sabin began trials of an oral vaccine. The oral vaccine was licenced in 1962.

The oral vaccine was often given on a sugar cube.

Currently many developed countries give a series of polio vaccines to babies. It is not recommended to adults in developed countries because they have probably already encountered polio, but is given to adults in 3rd world or developing countries.

Wider Success and Issues

The polio vaccine has a very high success rate. The issue now is getting the vaccine to the world.

The WHO began a widespread Polio vaccine programme after it was introduced. By 1988 there were 350 000 cases reported worldwide. By 2012 the number was 223.

In 1990 the WHO believed 500 000 cases of paralysis had been stopped by the vaccine.

In 1993 China immunized 80 million children in two days. The following year only 5 cases of Polio were reported.

The Polio vaccination remains on the WHO’s most important vaccinations list.

Ronald Reagan announced May 6th 1985 to be ‘Jonas Salk Day’.