BEIRUT, April 11 (Reuters) - Lebanon launched a fourth round of polio immunisation on Friday, trying to prevent the disease spreading from neighbouring Syria along with the tide of refugees fleeing the three-year conflict.
Protection against polio requires several vaccinations but aid workers are concerned that coverage in Lebanon has been falling off because parents were unaware of the need for multiple inoculation.
The announcement earlier this week that polio had been detected in Iraq, the first of Syria's neighbours to be hit by the virus, has added to fears that it could spread further.
The campaign in Lebanon targets around 600,000 Syrian, Lebanese and Palestinian infants aged up to five.
"The first three rounds were very successful, but there have been diminishing returns," said Luciano Calestini, deputy representative in Lebanon for the UN children's agency UNICEF, which is carrying out the campaigns with Lebanese officials.
After reaching more than 95 percent of the targeted children at first attempt, the cover slipped to the mid-80s in the last round, he said.
"One dose is not protection. Parents are underestimating the risk to their children ... They don't realise that multiple vaccinations are important and often stop at one or two."
Calestini said the number of Syrians fleeing into Lebanon, which hosts the highest number of refugees, meant it was the country most at risk of a new outbreak.
The crippling infectious disease was eradicated from Lebanon and Syria at least 13 years ago, but it was confirmed in 17 children in Syria in October.
There is no cure for the disease, which invades the nervous system and can cause irreversible paralysis within hours. It can only be prevented through immunisation. (Reporting By Dominic Evans; Editing by Tom Heneghan)