Poliomyelitis commonly known as polio or infantile paralysis, is an infectious virus disease in the brain and spinal cord. It is usually spread through infected faecal matter entering the mouth or by ingesting food or water containing human faeces. The virus can within a few hours cause muscle weakness and subsequent paralysis. The disease most commonly attacks the legs, but may also involve the head, neck and diaphragm. Most people recover fully from polio, but in those with muscle weakness about 2-5% of the children and 15-30 % of the adults die.  In up to 70 % of the infections there are no symptoms. Years after recovery, post-polio syndrome may occur, with a slow development of muscle weakness.

Major polio outbreaks started to occur in the late 19th century, and continued during the 20th century throughout Europe. Denmark experienced a polio epidemic from 1952 till 1953 where 7000 individuals were affected – mostly children. More than 3000 were paralysed, and approximately 350 died within a short time. In 1961, Denmark was the first country in the world to offer all school children from 1st to 5th grade a free polio vaccination.

There are two types of polio vaccine: one that uses inactivated poliovirus and is administered via injection (IPV) and one that uses weakened poliovirus and is administered orally (OPV).

In 2016, only 42 people were infected by polio, and it is hoped that the vaccination efforts and early detection of causes will result in global eradication of the disease by 2018.