Progress Toward Regional Measles Elimination — Worldwide, 2000–2017

In 2010, the World Health Assembly set three milestones for measles prevention to be achieved by 2015: 1) increase routine coverage with the first dose of measles-containing vaccine (MCV1) among children aged 1 year to ≥90% at the national level and to ≥80% in every district; 2) reduce global annual measles incidence to less than five cases per million population; and 3) reduce global measles mortality by 95% from the 2000 estimate (1).* In 2012, the World Health Assembly endorsed the Global Vaccine Action Plan (GVAP), with the objective of eliminating measles§ in four of the six World Health Organization (WHO) regions by 2015 and in five regions by 2020. Countries in all six WHO regions have adopted goals for measles elimination by 2020. This report describes progress toward global measles control milestones and regional measles elimination goals during 2000–2017 and updates a previous report (2). During 2000–2017, estimated MCV1 coverage increased globally from 72% to 85%; annual reported measles incidence decreased 83%, from 145 to 25 cases per million population; and annual estimated measles deaths decreased 80%, from 545,174 to 109,638. During this period, measles vaccination prevented an estimated 21.1 million deaths. However, measles elimination milestones have not been met, and three regions are experiencing a large measles resurgence. To make further progress, case-based surveillance needs to be strengthened, and coverage with MCV1 and the second dose of measles-containing vaccine (MCV2) needs to increase; in addition, it will be important to maintain political commitment and ensure substantial, sustained investments to achieve global and regional measles elimination goals.

Immunization Activities

WHO and the United Nations Children’s Fund (UNICEF) use data from administrative records and vaccination coverage surveys reported annually by 194 countries to estimate coverage with MCV1 and MCV2 delivered through routine immunization services. During 2000–2017, estimated MCV1 coverage increased globally from 72% to 85% (Table 1), although coverage has remained 84%–85% since 2010, and considerable variation in regional coverage exists. Since 2013, MCV1 coverage has remained relatively constant in the African Region (AFR) (69%–70%), the Region of the Americas (AMR) (92%), the European Region (EUR) (93%–95%), and the Western Pacific Region (WPR) (96%–97%). During 2013–2017, MCV1 coverage increased from 78% to 81% in the Eastern Mediterranean Region (EMR) and from 84% to 87% in the South-East Asia Region (SEAR). WPR is the only region to achieve and sustain >95% MCV1 coverage since 2006. Among the 73 countries that receive funding through Gavi, the Vaccine Alliance (Gavi-eligible countries),** MCV1 coverage increased during 2000–2017, from 59% to 79% (Table 1). Globally, 118 (61%) countries achieved ≥90% MCV1 coverage in 2017, an increase from 85 (44%) countries in 2000, and a slight decrease from 120 (62%) countries in 2016. During 2000–2017, the largest increases in the percentage of countries with ≥90% MCV1 coverage were in AFR (from 9% to 34%) and SEAR (from 27% to 64%); among Gavi-eligible countries, the percentage of countries with ≥90% MCV1 coverage increased from 15% to 44% (Table 1). In 2017, 78 (40%) countries reached ≥95% MCV1 coverage nationally, and 45 (23%) countries achieved ≥80% MCV1 coverage in all districts. Globally, an estimated 20.8 million infants did not receive MCV1 through routine immunization services in 2017. The six countries with the most unvaccinated infants were Nigeria (3.9 million), India (2.9 million), Pakistan (1.2 million), Indonesia (1.2 million), Ethiopia (1.1 million), and Angola (0.7 million).

Estimated MCV2 coverage increased globally from 15% in 2000 to 67% in 2017, largely because of an increase in the number of countries providing MCV2 nationally from 98 (51%) in 2000 to 167 (86%) in 2017 (Table 1). Three countries introduced MCV2 in 2017 (Laos, Namibia, and Nicaragua). During 2000–2017, the largest increases in regional MCV2 coverage were from 3% to 77% in SEAR, and from 2% to 94% in WPR. Among Gavi-eligible countries, MCV2 coverage increased from 2% to 51% during 2000–2017.

During 2017, approximately 205 million persons received supplementary doses of measles-containing vaccine (MCV) during 53 supplementary immunization activities (SIAs)†† implemented in 39 countries (Table 2). Based on doses administered, SIA coverage was ≥95% in 26 (49%) SIAs. During 2010–2017, a total of 1,476,826,523 persons were vaccinated globally through 443 measles SIAs (an average of 55 SIAs per year); 172 (39%) SIAs included at least one other health intervention.

Reported Measles Incidence

In 2017, 189 (97%) countries conducted measles case-based surveillance in at least part of the country, and 191 (98%) had access to standardized quality-controlled testing through the WHO Global Measles and Rubella Laboratory Network. However, surveillance was weak in many countries, and fewer than half of the countries reporting surveillance indicators (73 of 152; 48%) achieved the sensitivity indicator target of two or more discarded measles and rubella§§ cases per 100,000 population.

Countries report the aggregate number of incident measles cases¶¶,*** to WHO and UNICEF annually through the Joint Reporting Form.††† During 2000–2017, the number of measles cases reported worldwide decreased 80%, from 853,479 in 2000 to 173,330 in 2017, and measles incidence decreased 83%, from 145 to 25 cases per million population (Table 1). Compared with the reported number of cases (132,328) and incidence (19 cases per million) in 2016, both cases and incidence increased in 2017, in part because eight more countries reported case data in 2017 (184 of 194; 95%) than did in 2016 (176 of 194; 91%).§§§ The percentage of reporting countries with annual measles incidence of <5 cases per million population increased from 38% (64 of 169) in 2000 to 69% (122 of 176) in 2016, and then decreased to 65% (119 of 184) in 2017. During 2016–2017, reported measles cases increased 31% globally, 100% in AFR, 6,358% in AMR, 481% in EMR, 458% in EUR, and 3% in SEAR, but decreased 82% in WPR. In Gavi-eligible countries, reported cases increased 45% from 2016.

Genotypes of viruses isolated from measles cases were reported by 76 (59%) of the 129 countries that reported at least one measles case in 2017. Among the 24 recognized measles virus genotypes, 11 were detected during 2005–2008, eight during 2009–2014, six in 2015, and five in 2016 and 2017, excluding those from vaccine reactions and cases of subacute sclerosing panencephalitis, a fatal progressive neurologic disease caused by persistent measles virus infection (3).¶¶¶ In 2017, among 5,789 reported measles virus sequences,**** 2,641 (45.6%) were genotype B3 (53 countries); 15 (0.26%) were D4 (two countries); 2,542 (43.9%) were D8 (49 countries); 46 (0.80%) were D9 (six countries); and 545 (9.4%) were H1 (11 countries).

Measles Mortality Estimates

A previously described model for estimating measles disease and mortality was updated with new measles vaccination coverage data, case data, and United Nations population estimates for all countries during 2000–2017, enabling derivation of a new series of disease and mortality estimates. For countries with previously anomalous estimates, the model was modified slightly to generate mortality estimates consistent with the observed case data (4). Based on the updated data, the estimated number of measles cases declined from 28,493,539 (95% confidence interval [CI] = 19,808,871–64,780,514) in 2000 to 6,732,904 (CI = 2,950,042–36,842,865) in 2017. During this period, estimated measles deaths decreased 80%, from 545,174 (CI = 368,236–913,226) in 2000 to 109,638 (CI = 46,123–376,619) in 2017 (Table 1). During 2000–2017, compared with no measles vaccination, measles vaccination prevented an estimated 21.1 million deaths globally and 19.3 million deaths among Gavi-eligible countries (Figure) (Table 1).

Regional Verification of Measles Elimination

In 2017, AFR and EMR established regional verification commissions (RVCs); thus, all six regions now have RVCs. In September 2016, the AMR RVC declared the region free of endemic measles (5). In 2017, the EUR RVC verified measles elimination in 37 (70%) countries and the reestablishment of endemic measles virus transmission in the Russian Federation and in Germany (6). In SEAR, Maldives and Bhutan were verified as having eliminated measles in 2017 (7). In WPR, six (22%) countries (Australia, Brunei, Cambodia, Japan, New Zealand, and South Korea) and two areas, Hong Kong Special Autonomous Region (China) and Macao Special Autonomous Region (China), had verified measles elimination in 2017 (8). No EMR or AFR countries had verified elimination in 2017.

Discussion

During 2000–2017, increased coverage with MCV administered through routine immunization programs and SIAs, and other global measles elimination efforts contributed to an 83% decrease in reported measles incidence and an 80% reduction in estimated measles mortality. Measles vaccination prevented an estimated 21.1 million deaths during this period; the large majority of deaths averted were in AFR and among Gavi-eligible countries. Global MCV2 coverage has steadily increased since 2000; in 2017, 167 (86%) countries provided MCV2. In 2017, MCV1 and MCV2 coverage in WPR was ≥94%, and measles incidence in this region was at an all-time low. The increasing number of countries verified as having achieved measles elimination indicates progress toward global interruption of measles virus transmission.

Despite this progress, however, the 2015 global milestones have not been achieved; global MCV1 coverage has stagnated for nearly a decade; global MCV2 coverage is only at 67% despite steady increases; and SIA quality was inadequate to achieve ≥95% coverage in several countries. Since 2016, measles incidence has increased globally and in five of the six WHO regions. Furthermore, as of July 2018, endemic measles has been reestablished in Venezuela because of the sustained transmission of measles virus for >12 months; the remaining 34 AMR countries continue to maintain their measles elimination status, but the ongoing outbreak in Venezuela has led to measles virus importations and outbreaks in bordering AMR countries. In addition, the measles resurgence in Europe has likely led to reestablished endemic measles in some EUR countries. These outbreaks highlight the fragility of gains made toward global and regional measles elimination goals. Continuing to increase MCV1 and MCV2 coverage is critical to both the achievement and sustainability of the global and regional measles elimination goals. Meanwhile, conducting high quality SIAs that reach unvaccinated and undervaccinated children will prevent future outbreaks that are costly in terms of morbidity and mortality and are disruptive to immunizations service delivery. It is important to have high-performing surveillance for early detection of outbreaks; and when outbreaks do occur, thorough outbreak investigations are needed to better understand and address the underlying causes of the outbreak and why children are being missed by immunization delivery systems.

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The findings in this report are subject to at least three limitations. First, SIA administrative coverage data might be biased by inaccurate reports of the number of doses delivered, doses administered to children outside the target age group, and inaccurate estimates of the target population size. Second, large differences between the estimated and reported incidence indicate variable surveillance sensitivity, making comparisons between countries and regions difficult to interpret. Finally, the accuracy of estimates from the measles mortality model is affected by biases in all model inputs, including country-specific measles vaccination coverage and measles case-based surveillance data.

Monitoring progress toward measles elimination goals could be improved by establishing updated indicators. For example, the WHO Strategic Advisory Group of Experts on Immunization recently approved country classifications, and updates to the framework for the verification of measles elimination will standardize monitoring of countries’ progress toward verified elimination (9). Moreover, synergizing future global health efforts and capitalizing on immunization partners’ investments could be enhanced by dovetailing measles and rubella elimination strategies with post-GVAP immunization targets and strategies.

Strengthening routine immunization and continuing to conduct high-quality SIAs will help achieve global and regional measles elimination goals, improve overall vaccination coverage and equity, and assist in attaining universal health coverage. It is important that countries continue to strengthen case-based surveillance and increase MCV1 and MCV2 coverage and that immunization partners continue to raise the visibility of measles elimination goals and secure political commitment to these goals and sustained investments in health systems.

Corresponding author: James L. Goodson, jgoodson@cdc.gov, 404-639-8170.

CDC

 

By |2018-12-01T19:38:47+00:00December 1st, 2018|

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