The number of measles cases in the Region declined from over 185,000 in 1990 to 24,957 in 2015 [10] (see Fig. 1). The number of reported rubella cases declined from 29,617 in 2012 to 2 437 in 2015 [10]. Data submitted by countries show that 2 535 measles cases were reported in 33 countries while 1 090 rubella cases were reported in 17 countries in the Region during the first three-quarters of 2016 [WHO surveillance database, data not published]. Compared to the same period in 2015, the Region has seen an 89% reduction in the number of reported measles cases and an 80% reduction in the number of reported rubella cases in 2016. In both years fewer countries reported rubella cases (including zero reporting) than measles cases [10,11].

Despite significant efforts made by countries to improve the notification of cases, some national surveillance systems in the Region still fail to investigate and report every suspected case of measles or rubella. Therefore no laboratory testing is conducted to confirm the diagnosis of many fever and rash cases. At this stage of elimination, incomplete case investigations remain a concern throughout the Region.

All WHO Member States are expected to report routine vaccination coverage data to WHO and the United Nations Children’s Fund (UNICEF) in a standardized Joint Reporting Form. All 53 countries in the Region have introduced two doses of measles-rubella vaccination in their national childhood immunization schedules [12], and in 2015, all but two reported their routine vaccination coverage. Analysis of this data showed that 25 of the 51 reporting countries achieved the WHO-recommended coverage of greater than 95% for the first dose of measles-containing vaccine (MCV1) and 15 countries achieved this target for the second dose of measles-containing vaccine (MCV2) [13].

In 2015, five countries (Azerbaijan, Cyprus, Georgia, Kazakhstan, Kyrgyzstan) conducted different varieties of supplementary immunization activities (SIAs) covering various age groups using measles (M), measles-rubella (MR) or measles-mumps-rubella (MMR) vaccine. Azerbaijan, Cyprus and Kyrgyzstan have attained coverage of more than 85% in these activities. Kyrgyzstan reported more than 90% in both SIAs conducted [13] (see Figs. 2 and 3).

Widespread outbreaks of measles and rubella have been reported by just a few countries in the Region in the recent years. Large-scale measles outbreaks in 2015 were reported by Bosnia and Herzegovina, Germany, Kyrgyzstan and the Russian Federation [10]. Over half of the laboratory-confirmed measles cases in 2015 were predominantly among adolescents and young adults while 20% were among infants less than 12 months of age. Only 15% had received two doses of measles vaccine, 29% were not immunized, 11% were incompletely immunized and 45% had an unknown immunization status. Rubella outbreaks in 2015 were reported by Georgia, Kyrgyzstan, Poland and Ukraine [10,14], with the majority of cases reported among children less than 15 years of age. The countries’ immunization response following the measles-outbreaks varied from raising awareness among health physicians and parents to post-exposure vaccination and conducting catch-up vaccinations in the affected areas [14] (see Figs. 4 and 5).

Some countries reporting both sporadic and widespread measles cases in recent years have also reported high national measles vaccination coverage. A considerable proportion of these cases had not been fully vaccinated. Despite reportedly high vaccination coverage at national level, pockets of sub-optimal vaccination coverage in the Region persist. Since 2010, outbreaks have been reported in particular population groups in the region, where there is a lower probability of being vaccinated: Roma communities in Bulgaria, Anthroposophists in Germany, the Netherlands and Switzerland, Jewish ultra-orthodox communities in Belgium, Israel, United Kingdom and orthodox Protestants in the Netherlands [15–17]. However, large outbreaks reported in France (2011), United Kingdom (2014) and Germany (2015) revealed the vulnerability of certain age groups in the general population that had not benefited from vaccination due to varied reasons.

Furthermore, susceptible health care workers (HCWs) [14,17] played an important role in nosocomial infection in a few of the measles outbreaks in the Region. Approximately 68 HCWs in the Czech Republic, 13 HCWs in Latvia and 30 in Spain were affected in 2014 and 9 were affected in Croatia in 2015 [14,17]. Most of the affected HCWs were either unvaccinated or their vaccination status was unknown. Most countries in Europe do not have a measles vaccination requirement for HCWs and even those which recommend such, the policies are variably implemented [18].

Over the past few years, countries have undertaken several steps to strengthen both the epidemiological and laboratory components of their surveillance system but the quality of the existing surveillance varies considerably across the Region.

The WHO Regional Office for Europe (Regional Office) receives monthly reports of measles and rubella cases from Member States, which include case-based and aggregate reporting with both clinical and laboratory confirmation of the cases. Rubella and CRS surveillance, however, remain a challenge with only a few countries having an established system for monitoring and reporting.

A critical component of laboratory surveillance is the genetic characterization of wild-type measles and rubella viruses [19]. The genotyping data of the detected viruses provide evidence to document the interruption of endemic transmission of measles and rubella. However, the genotype reports alone do not sufficiently indicate the global or regional distribution of the viruses, as there is a strong bias in reporting of the data to the sequence database for measles and rubella [19]. Genetic data of the detected viruses should be combined with case-based epidemiological data to determine the transmission pathways of the circulating virus chains [20].

The measles and rubella laboratories in the European Region are part of the global WHO measles and rubella laboratory network, which provides confirmation of suspected cases of measles and rubella including genetic characterization of the circulating strains of identified wild-viruses. All (71) measles and rubella reference laboratories in the Region have retained their annual accreditation status through to 2015.

Molecular genotyping of the viruses has become increasingly important at this stage of the elimination process in European Region. Most countries with confirmed measles cases have submitted genomic sequence information to the measles nucleotide surveillance database; however, only a few countries with confirmed rubella cases have submitted genomic sequence information on rubella cases to the rubella nucleotide surveillance database [21]. Analysis of the available genotypic information indicates that a few of the measles genotypes are no longer detected in the European Region, thereby suggesting that several long-lasting transmission chains have been interrupted. This underlines the progress made by the Region towards measles elimination (see Fig. 6). Measles genotypes C2 and D7 have not been detected since 2004, and genotype D6 and a subvariant of D4 (Bucharest. ROU/48.04) have not been detected since 2007 [22]. Since 2012, genotypes B2, B3, D4, D8, D9, G3 and H1 have been detected in the European Region, of which B3, D4 and D8 have been predominant and the others have been detected sporadically in a few countries [22]. The measles genotypes identified in 2015 were B3, D4, D8, D9, and H1 [23]. The predominant measles genotypes reported in 2015 included several lineages of D8 reported by 27 countries and the variants of measles genotype B3 reported by 16 countries [14]. The major rubella genotypes identified in 2015 were 2B, 1E and 1a [24].

The European Regional Verification Commission for Measles and Rubella Elimination (RVC), an independent panel of experts, was established in 2011 [25] to evaluate the status of measles and rubella elimination in the Region based on the September 2010 resolution by the WHO Regional Committee for Europe. The vaccine-preventable diseases and immunization programme (VPI) of the Regional Office serves as the secretariat of the RVC.

The verification process involves examination of the evidence presented by each country’s national verification committee (NVC) based on the WHO-recommended performance indicators for both surveillance and immunization coverage [26]. As part of the verification process in the Region, each country submits documentation to RVC every year; a process which will continue for at least three years after the RVC confirms the interruption of endemic measles and rubella transmission in all Member States of the Region. The evaluation of the countries by the RVC according to the established criteria outlined verification framework for measles and rubella elimination in the WHO European Region is evidence-based, measurable and independent.

The RVC reviews information on measles and rubella epidemiology, molecular data, population immunity, and surveillance and classifies the countries according to WHO’s definition of elimination, i.e., the absence of endemic measles or rubella cases in a geographic area for a period of at least 12 months or more in the presence of a well-performing surveillance system [26]. Elimination can be verified once a country has sustained interruption of endemic transmission for 36 consecutive months. According to the verification framework for measles and rubella elimination in the Region, the endemic measles or rubella transmission will be considered reestablished when the epidemiological and laboratory evidence indicate that a chain of transmission of a virus variant has continued uninterrupted for a period of 12 months or more in a defined geographical area where the disease was previously eliminated [27]. By the end of 2015, none of the countries of the Region were found to have reestablished endemic measles or rubella transmission. The review of the measles/rubella elimination status in other WHO Regions shows that two countries namely Brazil in WHO Region of Americas and Mongolia in WHO Western Pacific Region were verified to have reestablished endemic measles transmission by their respective regional verification commissions in recent past [28,29].

In 2014, the verification procedures were modified by the RVC to allow verification of elimination at the national level as opposed to only at the regional level [30]. Similarly, the RVC revised the Annual Status Update reports (ASU) to include information on effective linkages between laboratory and epidemiological surveillance as well as documentation on chains of transmission [30].

The September 2010 resolution also urged each Member State to establish an NVC [8]. As of December 2016, 51 out of 53 countries have functioning NVCs [31], including the Scandinavian Verification Committee established by Denmark, Norway and Sweden. Monaco and San Marino have not established NVCs.

Following its review of the 2015 reports submitted by the NVCs, the RVC concluded that by 2015, 24 countries had eliminated measles and another 13 had interrupted endemic measles transmission; 24 had eliminated rubella and another 11 had interrupted endemic rubella transmission [31].

Recognizing the need for accelerated actions by countries and scaled-up support from WHO and other partners towards achieving the Region’s measles and rubella elimination target, the Regional Office introduced a package of accelerated actions in 2013 [32] to step up the support in high-priority countries. The RVC members and Regional Office staff conducted advocacy and technical missions to these countries [21], where country-specific issues were identified and the necessary technical support was provided. In 2014 and 2015, teams visited Austria, Bulgaria, Croatia, Cyprus, France, Greece, Italy, the Russian Federation and Spain; and in 2015, outbreak support was provided to Bosnia and Herzegovina, Kazakhstan and Kyrgyzstan [21]. In August 2016, WHO conducted a technical consultation with the United States Centers for Disease Control and Prevention (CDC) and European Centre of Disease Prevention and Control (ECDC) to review the situation of measles and rubella in endemic countries of the Region and identify priority elimination activities in these countries. A draft global measles-rubella categorization method [33] was used to identify specific determinants (immunization status and surveillance performance). This continuum exercise was planned to further enhance the support to the identified priority countries in the WHO European region. Country profiles outlining the challenges, interventions and priority activities are being developed following this consultation and will be shared with countries to scale up support and accelerate the elimination efforts in each of these measles and rubella endemic countries.