JUBA, South Sudan (AP) — Fifteen young children have died in a botched measles vaccination campaign that saw people as young as 12 years old administering the vaccines, South Sudan’s government announced Friday.

The United Nations said the children died of “severe sepsis/toxicity” from the contaminated vaccine, and the health ministry blamed the deaths on human error. One syringe was used for all the children during the four-day campaign, and the vaccine was stored without refrigeration the entire time.

Measles is yet another challenge facing the desperately poor East African country that already has been devastated by more than three years of civil war and a recently declared famine, as well as a cholera outbreak.

The government said all of the children who died were under the age of 5. It is setting up a commission to determine who is responsible and whether victims’ families will be compensated.

The measles vaccination campaign is targeting more than 2 million children across the country. About 300 children were targeted in the area where the children’s deaths occurred.

The children died in the rural town of Kapoeta in early May. Another 32 children suffered fever, vomiting and diarrhea but recovered, a joint statement by the World Health Organization and the U.N. children’s agency UNICEF said.

Abdulmumini Usman, the South Sudan country director for the World Health Organization, told The Associated Press earlier this week that even after the organization became aware of the deaths, the measles campaign continued across the country except in Kapoeta.