"We shouldn't be in this position in 2019 when we have had a safe and inexpensive vaccine for decades," he said. "We're seeing outbreaks in very different contexts and different types of countries ... irrespective of income level of country."

"The fact that any child dies from a vaccine-preventable disease like measles is frankly an outrage and a collective failure to protect the world's most vulnerable children," Dr. Tedros Adhanom Ghebreysus, director-general of the World Health Organization, said in a press release that accompanied the new report.

"To save lives, we must ensure everyone can benefit from vaccines - which means investing in immunization and quality health care as a right for all," he said.

The report estimated that during 2000 to 2018, measles vaccination averted about 23.2 million deaths.

The report found that the estimated number of measles deaths decreased 73% globally, falling from 535,600 in 2000 to 142,300 deaths in 2018.

The report also found that, during that same time period, the number of reported measles cases dropped 59%, from 853,479 to 353,236 cases, and measles incidence decreased 66%.

Yet in just the past couple of years, between 2016 and 2018, the reported number of cases and incidence actually increased, rising from 132,413 cases in 2016. Compared with 2016, the number of measles cases increased 167% globally, according to the report.

The report estimated that, between 2000 and 2018, the percentage of people who received their first dose of the measles vaccine increased globally from 72% to 86%. The percentage of people worldwide who received their second dose of the measles vaccine increased from 18% to 69%, largely because of an increase in the number of countries providing a second dose, according to the report.

"This report proves there is stagnation in coverage," Nandy said.

"Each year, children who are unvaccinated contribute to the number of susceptible children in communities and their continued accumulation results in outbreaks," he said. "This is a crisis and needs to be taken as a warning sign to improve the performance of immunization programs globally."

"So the fact that measles is now returning in some areas is an indication that our vaccine ecosystem is fragile and in some areas breaking down despite general gains," he said.

Hotez added that, no matter where you are in the world, there are specific factors that can play a role in driving the resurgence of measles: war, political collapse, climate change and anti-science or anti-vaccination movements.

Some areas that have seen a combination of those factors include Venezuela, Democratic Republic of Congo, Philippines, Arabian Peninsula and Samoa, he said, adding, "Therefore I believe we need to urgently reassess this situation and recognize the importance of confronting these determinants, especially the anti-vaccine movement."

Because of the outbreak, schools have been closed indefinitely since mid-November and children have been banned from public gatherings and places were people congregate.

More than 4,200 cases of measles have been reported across the Pacific island nation in recent weeks, including 62 deaths -- with two fatalities in the last 24 hours, according to official statistics. None of the victims were vaccinated, the government said.