Worldwide measles cases surged 17 percent so far this year amid stagnating immunization rates, the World Health Organization said on Friday.

"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," said Dr. Tedros Adhanom Ghebreysus, director-general of the WHO.

The increase comes as immunization rates languish, falling short of the 95 percent required to protect communities from the deadly disease, the organization said. Only an estimated 86 percent of children receive the first dose of the vaccine globally and fewer than 70 percent receiving the second dose.

More than 413,000 cases were reported this year, surpassing the 353,236 seen in all of 2018, the WHO added in its statement.

Reported cases are dwarfed by estimated ones. New estimates calculated by the WHO and the U.S. Centers for Disease Control and Prevention to reflect unreported cases worldwide show that in 2018, more than 9.7 million people were infected and more than 142,000 died — mostly children under the age of five.

The figures are a marked increase from 2017 estimates of nearly 7.6 million cases and 124,000 deaths.

With an effective vaccine available for over 50 years, health officials are calling the persistent spread unacceptable.

"These estimates remind us that every child everywhere needs — and deserves — this life-saving vaccine. We must turn this trend around and stop these preventable deaths by improving measles vaccine access and coverage," said Dr. Robert Linkins, who leads vaccine initiatives for the Centers for Disease Control.

The vaccine is attributed to saving more than 23 million lives in the last 18 years.

Victims of ethnic violence prepare the burial of a child suspected to have died of measles at a makeshift camp in the Democratic Republic of Congo in June. Olivia Acland / Reuters file

The five hardest-hit countries in 2018, which accounted for nearly half all the measles cases worldwide, were Ukraine, Liberia, Madagascar, Somalia and the Democratic Republic of Congo — which is also grappling an Ebola outbreak.

DRC is struggling yet again in 2019 to combat the spread of measles, reporting more than 250,000 cases this year — marking a three-fold increase from last year's figures.

"Sadly, measles has claimed more Congolese lives this year than Ebola. We must do better at protecting the most vulnerable, who are often also the hardest to reach," said Thabani Maphosa, managing director of country programs for vaccine health alliance Gavi, in a statement Thursday.

While sub-Saharan Africa was among the hardest-hit regions, wealthier countries were also failing to prevent the spread of measles.

The United States reported its highest number of cases in 25 years. More than 1,200 cases were reported in the first 10 months of 2019, according to the Centers for Disease Control.

Meanwhile in Europe, Albania, Czechia, Greece and the United Kingdom lost their measles elimination status following a series of outbreaks.

Measles infections are not only deadly.

The illness can have longer-term negative implications on children's health by damaging their immune system for months or even years, making them vulnerable to other deadly diseases like influenza, the WHO said. It can also result in permanent brain damage, blindness or hearing loss.