Polio outbreak in Syria sparks WHO vax campaign
The campaign will be largest-ever immunisation response in the region, WHO and the UN children's fund said in a joint statement on Monday.
WHO has said the vaccinations would take place in Egypt, Iraq, Jordan, Lebanon, the West Bank and the Gaza Strip, and Turkey.
Syrian refugees fleeing their country's conflict have taken shelter in surrounding states, particularly Lebanon, Jordan, Turkey and Iraq.
The vaccination campaign comes after the discovery of polio in Syria for the first time since 1999.
At least 17 children had been paralysed by polio, 15 of them in the eastern province of Deir ez-Zor, large swathes of which are under rebel control.
The other two cases were recorded in Aleppo in the north, and in Douma, near the capital Damascus.
"Inside Syria, the campaign aims to reach 2.2 million children, including those who live in contested areas and those who were missed in an earlier campaign," the statement said.