Polio: World Health Organisation launches new vaccine swap to eradicate the previous few strains in the disease

Over the next two weeks, some 150 countries will take part in a synchronised switch to a two-strain vaccine which tackles all of those other variations in the wild polio virus - type 1 and type 3.

The transmission of type 2 polio was eradicated in 1999, meaning immunising against it now's pointless.

There are actually rare times when the vaccine - containing a live weakened kind of type 2 polio - has mutated and increase the risk for patient contracting herpes, and so the end to vaccinating against it removes that risk.

Following 30 years in the successful immunisation programme, just 12 cases were recorded worldwide this year, in Pakistan and Afghanistan, and experts predict the problem could be destroyed permanently inside a decade.

Africa remains entirely free in the disease for more than a year.

If the campaign succeeds, polio might be the second disease being eradicated since smallpox was declared extinct in 1980.