More than 20 million children are to be vaccinated in Syria and neighbouring countries against polio to try to stop the spread of the crippling infectious disease following its re-emergence there after 14 years, United Nations agencies said on Friday (November 8).

The mass vaccination against polio, which can spread rapidly among children, is already under way in the Middle East a week after the region declared a polio emergency, the World Health Organisation (WHO) and the U.N. Children's Fund (UNICEF) said.

Aiming to repeatedly vaccinate about 20 million children in seven countries and territories, it will be the largest-ever consolidated immunisation response in the Middle East.

The nationwide polio vaccination campaign in neighbouring Lebanon started on Friday, targeting more than 750,000 children aged under five.

"Today was the launching of the polio campaign in Lebanon. Lebanon has been polio-free for almost twelve years and it should stay as it is. Therefore today, together with the ministry of health, we have started the vaccination of more than 750,000 under five children," UNICEF representative in Lebanon, Anna Maria Laurini said.

There is no cure for polio, a highly infectious disease which invades the nervous system and can cause irreversible paralysis within hours. It can only be prevented through immunisation.

The WHO said initial tests had come back positive for polio in two of the 22 cases in Syria and final laboratory results were likely to confirm the presence of the virus.

"We are now in one of the tent settlements that are getting Syrian refugees and the vaccination is across the country so it is in border points, it is in the tented settlement as the one that you see here, and it is in all public health facilities, all shelters and then door to door. All the children under five, irrespective nationalities, are vaccinated," said Laurini.

Aid workers said doctors would vaccinate the children in Lebanon regardless of whether they had been treated before and would mark each child's finger with a long-lasting ink stain.

Presented by Adam Justice