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Discussion

After the 2005 WHO Regional Committee resolution that called for regional elimination of rubella and CRS, EUR has made substantial progress with high reported regional RCV coverage, low rubella incidence, and verification that nearly all countries have achieved elimination of endemic transmission of rubella viruses. EUR countries have shown their commitment to the elimination of measles and rubella and CRS with the Regional Committee resolution in 2005 and reaffirmed that commitment with resolutions in 2010 and 2014 (13). All EUR countries have longstanding 2-dose routine RCV immunization schedules that have provided a substantial foundation for establishing population immunity against rubella viruses. Regional rubella coverage with the first and second doses of RCVs has exceeded 93% and 80%, respectively, for the past 10 years. Immunization gaps account for sporadic rubella cases reported in 2019 and have not resulted in confirmed ongoing transmission of rubella viruses.

One of the considerable challenges with verifying rubella elimination has been classifying the large number of clinically compatible rubella cases. In part because rubella is typically a mild disease, a laboratory test is not always performed to confirm a diagnosis, and testing varies considerably across the region according to public health systems, clinical practice, and laboratory capacities. Without a confirmatory laboratory test result, suspected cases are classified as clinically compatible. Increased testing and efficiencies of subnational laboratory networks have contributed to improvements in the surveillance indicators and case classification, but additional efforts are needed.

Rubella population immunity estimates across the region based on longstanding national immunization coverage rates are well above the rubella herd immunity threshold of 83%–86%, which should disrupt chains of transmission and stop or slow the spread of disease (10). However, subnational immunization gaps pose a risk for importation and circulation of rubella viruses. Efforts to eliminate endemic transmission of rubella have benefited substantially from the national and subnational outbreak response immunization campaigns for measles cases with combined measles- and rubella-containing vaccines, particularly for large measles outbreaks during 2017–2020.

Retrospective rubella reviews for the verification process provided an opportunity to focus on the specific documentation needed to support the elimination of endemic rubella virus transmission and consisted of an in-depth analysis of information provided in the annual status update reports and supplementary information from national immunization programs, surveillance networks, and the measles-rubella laboratory networks. The retrospective reviews were shared with the EU-RVC members on an ad hoc basis and provided an opportunity to ask for clarification or additional information before drawing conclusions about a country’s rubella elimination status. Data to complete the rubella retrospective reviews for the last four countries with endemic rubella transmission (Bosnia and Herzegovina, Italy, Poland, and Ukraine) are being collected, analyzed, and formatted for submission to the RVC for their determination.

The findings in this report are subject to at least three limitations. First, sensitivity of integrated measles and rubella surveillance might be lower for rubella than it is for measles because it is a milder illness, resulting in possible detection of fewer cases. Second, direct comparisons between countries might not be valid because of variations in their historic approach to diagnosis, case investigation, and laboratory testing. Finally, the region comprises countries with widely different population sizes and compositions, making regional successes and challenges difficult to measure.

Substantial progress toward rubella elimination has been made in EUR. Verification of elimination is nearly complete, which would make EUR the second WHO region to achieve rubella elimination, the first being the Region of the Americas. Sustaining regional rubella elimination will require maintaining high coverage with RCVs through routine immunization programs at the national and subnational levels, offering supplementary rubella vaccination to susceptible adults, maintaining high-quality laboratory-supported rubella and CRS surveillance for outbreak detection and response, and a fully functioning Regional Verification Commission. Because of the COVID-19 pandemic, additional efforts might be needed to strengthen surveillance systems and fill in the immunity gaps.

Source of original article: Centers for Disease Control and Prevention (CDC) / MMWR (Journal) (tools.cdc.gov).
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