Roughly 300,000 children were vaccinated against polio by South Sudan’s Ministry of Health, according to the World Health Organization.

The vaccination was part of a four day campaign that sought to overcome conflict across the country.

“The commitment of health teams to reach as many children as possible in difficult circumstances is really to be commended,” said the WHO Representative to South Sudan Dr Abdulmumini Usman.

The campaign aims to reach 3.5 million children across the country aged 0-59 months, but the WHO said that South Sudan’s conflict made the immunization process more difficult.

“Delivering polio vaccines in South Sudan has never been harder, however insecurity, ongoing clashes and displacement made the logistical arrangement overwhelming,” the organization said in a press release. “Vaccinators struggled with impossible burdens to find every child of the displaced families scattered in hard-to-reach areas, including besieged locations,”