Progress Toward Regional Measles Elimination — Worldwide 2000–2016

Tuesday, 31st of October 2017

MMWR

CDC

Progress Toward Regional Measles Elimination — Worldwide 2000–2016

Weekly / October 27 2017 / 66(42);1148–1153

Alya Dabbagh PhD¹; Minal K. Patel MD¹; Laure Dumolard PhD¹; Marta Gacic-Dobo MSc¹; Mick N. Mulders PhD¹; Jean-Marie Okwo-Bele MD¹; Katrina Kretsinger MD¹; Mark J. Papania MD²; Paul A. Rota PhD³; James L. Goodson MPH² (View author affiliations)

Summary

What is already known about this topic?

The fourth United Nations Millennium Development Goal adopted in 2000 set a target to reduce child mortality by two thirds by 2015. One indicator of progress toward this target was measles vaccination coverage.

What is added by this report?

For the first time annual estimated measles deaths were fewer than 100000 in 2016. This achievement follows an increase in the number of countries providing the second dose of measles-containing vaccine (MCV2) nationally through routine immunization services to 164 (85%) of 194 countries and the vaccination of approximately 119 million persons against measles during supplementary immunization activities in 2016. During 2000–2016 annual reported measles incidence decreased 87% from 145 to 19 cases per million persons annual estimated measles deaths decreased 84% from 550100 to 89780 and an estimated 20.4 million deaths were prevented. However the 2015 measles elimination milestones have not yet been met and only one World Health Organization region has been verified as having eliminated measles.

What are the implications for public health practice?

To achieve measles elimination goals countries and their partners need to act urgently to secure political commitment raise the visibility of measles elimination increase vaccination coverage strengthen surveillance and mitigate the threat of decreasing resources once polio eradication is achieved. Polio eradication resources have supported routine immunization services and surveillance activities.

The fourth United Nations Millennium Development Goal adopted in 2000 set a target to reduce child mortality by two thirds by 2015. One indicator of progress toward this target was measles vaccination coverage (1). In 2010 the World Health Assembly (WHA) set three milestones for measles control by 2015: 1) increase routine coverage with the first dose of a 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 <5 cases per million population; and 3) reduce global measles mortality by 95% from the 2000 estimate (2).* In 2012 WHA endorsed the Global Vaccine Action Plan^† with the objective of eliminating measles in four 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 or before 2020. Measles elimination is defined as the absence of endemic measles virus transmission in a region or other defined geographic area for ≥12 months in the presence of a high quality surveillance system that meets targets of key performance indicators. This report updates a previous report (3) and describes progress toward global measles control milestones and regional measles elimination goals during 2000–2016. During this period annual reported measles incidence decreased 87% from 145 to 19 cases per million persons and annual estimated measles deaths decreased 84% from 550100 to 89780; measles vaccination prevented an estimated 20.4 million deaths. However the 2015 milestones have not yet been met; only one WHO region has been verified as having eliminated measles. Improved implementation of elimination strategies by countries and their partners is needed with focus on increasing vaccination coverage through substantial and sustained additional investments in health systems strengthening surveillance systems using surveillance data to drive programmatic actions securing political commitment and raising the visibility of measles elimination goals.

Immunization Activities

To estimate coverage with MCV1 and the second dose of measles-containing vaccine (MCV2) through routine immunization services^§ WHO and the United Nations Childrens Fund (UNICEF) use data from administrative records (administrative coverage is calculated by dividing the vaccine doses administered by the estimated target population) and immunization coverage surveys reported annually by 194 countries. During 2000–2016 estimated MCV1 coverage increased globally from 72% to 85% (Table 1) although coverage has not increased since 2009. Considerable variability in regional coverage exists. Since 2012 MCV1 coverage has remained essentially unchanged in the African Region (AFR) (72%) the Region of the Americas (AMR) (92%) and the Eastern Mediterranean Region (EMR) (77%). In the European Region (EUR) MCV1 coverage has declined from 95% to 93% since 2012 with 51% of EUR member states reporting lower coverage since 2013. In the South-East Asia Region (SEAR) MCV1 coverage increased slightly since 2012 from 84% to 87%. The Western Pacific Region (WPR) is the only region that has achieved and sustained MCV1 coverage >95% (since 2008). Since 2000 the number of countries with MCV1 coverage of ≥90% increased globally from 85 (44%) in 2000 to 119 (61%) in 2015 and to 123 (63%) in 2016. However among countries with ≥90% MCV1 coverage nationally the percentage with ≥80% MCV1 coverage in all districts declined from 46% (52 of 112) in 2010 to 45% (49 of 110) in 2015 and 36% (44 of 123) in 2016. Among the estimated 20.8 million infants who did not receive MCV1 through routine immunization services in 2016 approximately 11 million (53%) were in six countries with large birth cohorts and suboptimal coverage: Nigeria (3.3 million) India (2.9 million) Pakistan (2.0 million) Indonesia (1.2 million) Ethiopia (0.9 million) and the Democratic Republic of the Congo (0.7 million).

During 2000–2016 the number of countries providing MCV2 nationally through routine services increased from 98 (51%) to 164 (85%) with four countries (Guatemala Haiti Papua New Guinea and Timor-Leste) introducing MCV2 in 2016. Estimated global MCV2 coverage steadily increased from 15% in 2000 to 60% in 2015 and 64% in 2016 (Table 1). During 2016 approximately 119 million persons received supplementary doses of measles-containing vaccine (MCV) during 33 mass immunization campaigns known as supplementary immunization activities (SIAs)^¶ implemented in 31 countries (Table 2). Based on doses administered SIA coverage was ≥95% in 20 (61%) SIAs. Among the six countries that conducted post-SIA coverage surveys estimated coverage was ≥95% in three 90%–94% in two and 84% in one.

Disease Incidence

Countries report the aggregate number of incident measles cases**^†† to WHO and UNICEF annually through the Joint Reporting Form. In 2016 189 (97%) countries conducted 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. Nonetheless surveillance was weak in many countries; fewer than half of countries (64 of 134; 48%) achieved the sensitivity indicator target of two or more discarded measles and rubella^§§ cases per 100000 population in 2016 compared with 2015 (80 of 135; 59%).

During 2000–2016 the number of measles cases reported annually worldwide decreased 85% from 853479 in 2000 to 214812 in 2015 and then to 132137 in 2016; measles incidence decreased 87% from 145 to 19 cases per 1 million population (Table 1). Compared with 2015 2016 incidence decreased from 29 to 19 cases per million although three fewer countries (173 of 194; 89%) reported case data in 2016 than did in 2015 (176 of 194; 92%).^¶¶ The percentage of reporting countries with fewer than five measles cases per million population increased from 38% (64/169) in 2000 to 69% (119/173) in 2016. During 2000–2016 measles incidence of fewer than five cases per million was sustained in AMR (Table 1).

During 2015–2016 the number of reported measles cases declined globally and in all regions (AFR 31%; AMR 98%; EMR 71%; EUR 84%; SEAR 44% and WPR 11%). In addition to aggregate reporting countries report measles case-based data to WHO monthly. In some countries large discrepancies exist between the two reporting systems. During 2016 some countries either did not report or reported only a fraction of monthly reported measles cases through the Joint Reporting Form (e.g. India reported 70798 measles cases through monthly reporting but only 17250 through the Joint Reporting Form).

Genotypes of viruses isolated from measles cases were reported by 60 (55%) of the 110 countries that reported at least one measles case in 2016. Among the 24 recognized measles virus genotypes 11 were detected during 2005–2008 eight during 2009–2014 six in 2015 and five in 2016 excluding those from vaccine reactions and cases of subacute sclerosing panencephalitis a fatal progressive neurologic disorder caused by persistent measles infection (4).*** In 2016 among 4796 reported measles virus sequences^††† 666 were genotype B3 (36 countries); 44 were D4 (four); 1407 were D8 (43); 87 were D9 (four); and 2592 were H1 (13).

Disease and 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 2000–2016 enabling derivation of a new series of disease and mortality estimates (5). Based on the updated data the estimated number of measles cases declined from 29068400 (95% confidence interval [CI] = 20606800–55859000) in 2000 to 6976800 (95% CI = 4190500–28657300) in 2016. During this period the number of estimated measles deaths declined 84% from 550100 (95% CI = 374000–896500) in 2000 to 89780 (95% CI = 45700–269600) in 2016 (Table 1). Compared with no measles vaccination measles vaccination prevented an estimated 20.4 million deaths during 2000–2016 (Figure).

Regional Verification of Measles Elimination

In 2016 four WHO regions had functioning regional verification commissions. In September 2016 the AMR regional verification commission declared the region free of endemic measles (6). In 2016 the EUR commission verified measles elimination in 24 countries (7). Two SEAR countries (Bhutan and Maldives) were verified as having eliminated measles in 2017 (8). The WPR commission reclassified Mongolia as having reestablished endemic measles virus transmission because of an outbreak that lasted >12 months; thus five WPR countries (Australia Brunei Cambodia Japan and South Korea) and two areas (Macao Special Autonomous Region [SAR] [China] and Hong Kong SAR [China]) had verified measles elimination status in 2016 (9).

Discussion

During 2000–2016 increased coverage with MCV administered through routine immunization programs worldwide combined with SIAs contributed to an 87% decrease in reported measles incidence and an 84% reduction in estimated measles mortality. Measles vaccination prevented an estimated 20.4 million deaths during this period and during 2016 for the first time ever estimated measles deaths declined to fewer than 100000. Furthermore the number of countries with measles incidence of fewer than five per million population has increased although considerable underreporting occurred and AMR has maintained an incidence of fewer than five cases per million population during 2000–2016. The decreasing number of circulating measles virus genotypes suggests interruption of some chains of transmission. However the 2015 global control milestones were not met global MCV1 coverage has stagnated global MCV2 coverage has reached only 64% and SIA quality was inadequate to achieve ≥95% coverage in several countries. With suboptimal MCV coverage outbreaks continued to occur among unvaccinated persons including school-aged children and young adults.

The 2016 Mid-term Review of the Global Measles and Rubella Strategic Plan 2012–2020 concluded that measles elimination strategies were sound and the WHO Strategic Advisory Group of Experts on Immunization endorsed its findings. The review noted however that implementation of the strategies needs improvement. Measures should focus on strengthening immunization and surveillance systems. The Measles and Rubella Initiative should increase its emphasis on using surveillance data to drive programmatic actions.

The findings in this report are subject to at least three limitations. First SIA 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 the results 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.

The decrease in measles mortality to fewer than 100000 deaths in 2016 is one of five main contributors (along with decreases in mortality from diarrhea malaria pneumonia and neonatal intrapartum deaths) to the decline in overall child mortality worldwide and progress toward the fourth United Nations Millennium Development Goal but continued work is needed to help achieve measles elimination goals (10). Of concern is the possibility that the gains made and future progress in measles elimination could be reversed when polio-funded resources supporting routine immunization services measles SIAs and measles surveillance diminish and disappear after polio eradication. Countries with the highest measles mortality rely most heavily on polio-funded resources and are at highest risk for reversal of progress after polio eradication is achieved. Improved implementation of elimination strategies by countries and their partners is needed with focus on increasing vaccination coverage with substantial and sustained additional investments in health systems strengthening surveillance systems using surveillance data to drive programmatic actions securing political commitment and raising the visibility of measles elimination goals.