London, UK (Reuters) – Gaps in vaccination coverage against measles have lead to several outbreaks of the highly–contagious disease in Europe in the past year, with both children and young adults affected, health officials said on Monday.

During the first two months of 2017, more than 1,500 measles cases were reported from 14 European countries due to "an accumulation of unvaccinated individuals," said officials from the European Centre for Disease Prevention and Control (ECDC).

In 10 countries, Austria, Belgium, Croatia, France, Germany, Italy, Poland, Romania, Spain and Sweden, the number of cases reported in January–February 2017 was more than double that of the first two months of 2016.

"It is unacceptable to hear that children and adults are dying from disease where safe and cost–effective vaccines are available," Vytenis Andriukaitis, the EU's health commissioner, said in response to the ECDC's data.

Measles is a highly contagious virus that spreads through direct contact and through the air. It can be prevented with a safe and effective vaccine, but due to immunization gaps remains one of the biggest killers of children worldwide.

The World Health Organization says measles killed 134,000 in 2015.

In the 12 months from March 1, 2016 to February 28, 2017, a total of 5,881 cases of measles were reported in Europe. Romania accounted for 46% of those, while 24% were in Italy and 9% in Britain.

The ECDC's report said one of the most concerning aspects of the recent outbreaks in Europe was that they were in older age groups as well as children. In 2015 and 2016 around a third of all measles cases in Europe were in adults over 20 years old.

"Closing immunization gaps in adolescents and adults who have not received vaccination in the past as well as strengthening routine childhood immunization programs will be vital to prevent future outbreaks," it said.

Public trust in immunization is an important global health issue, with lack of trust leading people to turn down potentially life–saving vaccines. Experts say negative attitudes may be due to controversies over suspected side–effects and hesitancy among some family doctors.

Many adults don't realize they are susceptible to vaccine preventable diseases such as measles, falsely believing that they only infect babies and school–age children.

Interrupting transmission of measles requires at least 95% vaccination coverage with two doses.

The latest data for 2015 showed vaccination coverage for the second dose of measles was below 95% in 15 out of 23 European Union/European Economic Area countries which reported figures, the ECDC said. Coverage for the first was below 95% in 12 of 27 countries who reported data.