In August, a World Health Organization (WHO) report revealed that more cases of measles have been recorded in Europe in the first half of 2018 than any full year of the past decade. The troubling surge in infections is the continuation of an outbreak that began in 2017; an estimated 23,937 children and adults contracted the highly contagious virus last year. So far this year, more than 41,000 patients have already been confirmed. Ukraine has been the hardest hit, with more than 23,000 cases, and France, Georgia, Greece, Italy, Russia, and Serbia have all seen at least 1,000 cases each.

Though most healthy adults can easily recover from the measles virus, it can be deadly in children under five and those who are weakened by malnutrition or a compromised immune system. However, thanks to an incredibly effective vaccine, measles is now a poster child for preventable diseases. Rigorous global vaccination programs launched in the 1980s slowed its spread significantly, and in 2016, measles was considered to be eradicated from the American continents and many European nations.

The only explanation for its recent reemergence is insufficient immunization. And while lack of access to medical care will always be a barrier to total coverage, researchers have identified the principal cause: Europe’s growing anti-vaccination sentiments.

Results from the 2016 State Of Vaccine Confidence survey, conducted by the London School of Hygiene and Tropical Medicine, reveal an alarming prevalence of vaccine distrust across many of the 67 nations that were included. When you compare the survey data to the outbreak data, the overlap tracks “quite neatly”, said Heidi Larson, director of the Vaccine Confidence Project, while speaking to BuzzFeed News.

Discussing the larger-picture implications of misplaced skepticism in vaccines, Larson added: “Measles is the canary in the coal mine that flags us to expect more outbreaks — of not just measles.”

According to her team’s findings, seven of the 10 countries with the worst perception of vaccines are European. France leads this sad pack, with 41 percent of respondents disagreeing with the statement “I think vaccines are safe.” Russian participants disagreed over 27 percent of the time, whereas the rates for Ukraine and Italy were 25 and nearly 21 percent. 

Maps of vaccine coverage compiled by the European Centre for Disease Prevention and Control (ECDC) shows that the overall proportion of residents who have received one or two doses of measles vaccine (one confers 93 percent protection, two confers 97 percent) as of 2017 is only 85 to 94 percent in many countries, including France and Italy. (Russia, Serbia, and Ukraine are not included in the monitoring). Past research has shown that extremely high coverage of 97 percent or above is needed to prevent outbreaks.

"If the coverage dips below [95percent] in certain regions, measles cases can spread and outbreaks can and are occurring," Dr Pauline Paterson, co-director of the Vaccine Confidence team, told CNN.

Of course, these broad statistics can’t account for every variable affecting measles transmission. For example, in America, overall coverage rates for the MMR vaccine are below the ideal threshold, hovering at about 94 percent according to the Centers for Disease Control and Prevention. And yet measles has returned to the US with significantly less vigor. So far in 2018, there have been only 124 confirmed cases.

But regardless of the mysteries underlying outbreak patterns, one truth remains.

"Vaccines work," Dr Paterson said. "If measles is to be eliminated, we must continue to further our understanding of the underlying reasons for non-vaccination and to address them with effective, evidence-based interventions."