"We must collectively respond, without further delay, to close immunization gaps," said Zsuzsanna Jakab, WHO's European director.
"It is unacceptable that, after the last 50 years' efforts to make safe and effective vaccines available, measles continues to cost lives, money and time."
According to the UN health agency, 22,149 cases of measles have been reported in seven countries across the region since the start of 2014, with Kyrgyzstan, Bosnia and Herzegovina as well as Russia hit hardest.
So far this year, there have been 47 cases of measles reported in Austria.
Despite a 95 percent immunization rate
of babies in Austria, cases of preventable diseases have been growing. In 2013, there were 74 measles cases. In 2014, that number increased to 114, a figure which is concerning medical professionals.
"That's a lot," says virologist Heidemarie Holzmann of the Medical University of Vienna.
Measles is often underestimated, says the expert. "Every fifth case experiences complications", she said.
In the worst case it can turn into encephalitis, a potentially fatal inflammation of the brain.
Statistics show that only two in every 1,000 patients die from a measles infection.
But the number of cases has rocketed recently in Berlin, with 447 already reported so far this year in the German capital.
Measles causes fever and rash and in severe cases can lead to pneumonia or brain swelling, which is sometimes fatal. The disease is highly contagious because it is transmitted through the air.
Even if the number of measles cases dropped by 50 percent from 2013-2014, the current epidemic has put into serious doubt the objective of eradicating the disease in Europe by the end of the year.
"The priority is now to control current outbreaks in all affected countries through immunization," Nedret Emiroglu, a deputy director in WHO's Europe office.
Many people who do not vaccinate their children say they fear a triple vaccine for measles, mumps and rubella (MMR) is responsible for increasing cases of autism -- a theory repeatedly disproven by various studies.