For the past three weeks, the Pacific island nation of 200,000 people has been in the grip of a measles epidemic that has been exacerbated by low immunization rates.

Schools were closed from Monday after the government declared an emergency on Saturday. The National University of Samoa also told students to stay home and said exams scheduled for this week had been indefinitely postponed.

Health authorities said most of those who died were under the age of 2. They counted 716 measles cases reported, with nearly 100 people still hospitalized including 15 in intensive care.

Samoa’s Director General of Health Leausa Take Naseri said in a news conference last week that he expects the epidemic will get worse. He said that only about two-thirds of Samoans had been vaccinated, leaving the others vulnerable to the virus.

But figures from the World Health Organization and UNICEF indicate that measles immunization rates among Samoan infants have fallen steeply from over 70% in 2013 to under 30% last year.

Helen Petousis-Harris, a vaccine expert at New Zealand’s University of Auckland, said the Samoan government halted its immunization program for several months last year after two infants died from a medical mishap involving a vaccine.

New Zealand Prime Minister Jacinda Ardern said Monday it was sending 3,000 vaccines to Samoa as well as nurses and medical supplies.

Ardern said Samoan authorities believe the outbreak was started by a traveler from New Zealand.

“We, of course, have an open flow of people,” Ardern said. “But we see our responsibility as supporting Samoa as they deal with the outbreak, and we are doing that actively.”

Petousis-Harris said it was disappointing that people in New Zealand who were carrying the virus had traveled to Samoa. She said New Zealand has for years known it has immunity gaps.

“But we didn’t deal with the problem,” she said.

Tonga, Fiji and New Zealand have also reported outbreaks of measles but on a smaller scale than in Samoa.