The United Nations agencies for health and children have launched a diphtheria vaccination campaign in war-torn Yemen targeting over 2.8 million children between the ages of six weeks and 15 years.

U.N. spokesman Stephane Dujarric said Thursday that over 4,000 Yemenis have gotten diphtheria since 2017 and more than 200 have died.

He says the World Health Organization and UNICEF report that preliminary data indicate that over 1 million children have been vaccinated within the first five days of the campaign.

Diphtheria is an infectious and contagious disease that usually involves the nose, throat, and air passages, but may also infect the skin.

Dujarric says more than 8,000 health workers and community volunteers are participating in the vaccination campaign in eight cities, including Hodeida, Al Jawf, Dhamar and Ibb.