Progress in Global Measles Control, 2000–2010

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In 1980, before widespread global use of measles vaccine, an estimated 2.6 million measles deaths occurred worldwide (1). In 2001, to accelerate the reduction in measles cases achieved by vaccination, the World Health Organization (WHO) and the United Nations Children's Fund (UNICEF) developed a strategy to deliver 2 doses of measles-containing vaccine (MCV) to all children through routine services and supplementary immunization activities (SIAs) and improved disease surveillance (2). After implementation of this strategy, the estimated number of annual measles deaths worldwide decreased from 733,000 in 2000 to 164,000 in 2008 (3). In 2010, the World Health Assembly endorsed the following measles objectives for 2015: 1) raise routine coverage with the first dose of MCV (MCV1) for children aged 1 year to ≥90% nationally and ≥80% in every district or equivalent administrative unit, 2) reduce and maintain annual measles incidence at <5 cases per million, and 3) reduce measles mortality by ≥95% from the 2000 estimate (4). During 2000–2010, global MCV1 coverage increased from 72% to 85% with approximately 1 billion children vaccinated during measles SIAs. Reported measles cases decreased from 2000 to 2008, remained stable in 2009, and increased in 2010. By the end of 2010, 40% of countries still had not met the incidence target of <5 cases per million. Key challenges must be overcome to meet the 2015 objectives, including 1) declining political and financial commitments to measles control, 2) failure to reach uniform high coverage with 2 doses of MCV through routine services or SIAs, and 3) inadequate monitoring subnationally of coverage with the first and second dose of MCV to guide interventions to increase coverage.

Immunization Activities

WHO and UNICEF use annual data from administrative records and surveys reported by countries to estimate MCV1 coverage administered through routine immunization services to children aged 1 year. Countries annually report the number of districts with ≥80% MCV1 coverage (5). During 2000–2010, estimated global MCV1 coverage increased from 72% to 85%; by 2010, three of six WHO regions had >90% estimated MCV1 coverage (Table 1). In 2010, 20,651 (61%) of 33,966 districts worldwide achieved ≥80% MCV1 coverage; 58 (30%) countries, representing 9% of the global population, reached the target in every district. Of the estimated 19.1 million children who did not receive MCV1 in 2010, 10.4 million (55%) were in five countries: India (6.7 million), Nigeria (1.7 million), Democratic Republic of the Congo (DRC) (0.8 million), Uganda (0.6 million), and Pakistan (0.6 million).

By 2010, all countries had provided a second opportunity for measles vaccination. The second dose of MCV was offered through routine services in 139 (72%) countries, including seven (15%) of 47 high-burden priority countries.* In 2010, MCV2 coverage among target-aged children, based on administrative records, was reported by 102 (73%) countries, and 67 (66%) of those countries reported ≥90% coverage. During 2000–2010, approximately 1 billion children received measles vaccination through SIAs. During 2009–2010, based on country reports, >323 million children in 55 countries were vaccinated during 63 SIAs, including 40 reaching >142 million children in 32 (68%) of 47 priority countries. Reported coverage was >90% for 46 (73%) SIAs, including 26 (72%) in priority countries (Table 2).

Surveillance Activities

The number of countries reporting annual measles surveillance data to WHO and UNICEF (6,7) increased from 169 (88%) in 2000 to 190 (98%) in 2010. Measles surveillance included case-based surveillance with laboratory testing to confirm cases and outbreaks. By 2010, 179 countries (83%) had implemented case-based surveillance, up from 120 (62%) in 2004,† and the number of countries supported with standardized quality-controlled testing by the WHO Measles and Rubella Laboratory Network increased to 183 (95%) from 71 (37%) in 2000.

From 2000 to 2010, annually reported measles cases decreased 60% worldwide, from 853,480 to 339,845, and measles incidence decreased 66% from 146 cases per million to 50 cases per million, with all WHO regions reporting decreases in cases and incidence (Table 1). The greatest decrease in reported measles cases was from 853,480 in 2000 to 277,968 in 2008 (Figure).

From 2008 to 2009, global reported measles cases remained stable, with increases in the African Region (AFR) from 37,012 to 83,479 and the Eastern Mediterranean Region (EMR) from 12,120 to 36,605 balanced by a decrease in the Western Pacific Region (WPR) from 147,987 to 66,609. In 2010, decreases in reported measles cases in WPR to 49,460, in EMR to 10,072, and in the South-East Asia Region (SEAR) from 84,356 to 50,265 were offset by increases in AFR to 199,174 and in the European Region (EUR) from 7,499 to 30,625, with reported measles cases increasing globally to 339,845. Globally, the percentage of countries with reported measles incidence <5 cases per million increased from 64 (38%) of 169 reporting countries in 2000 to 122 (67%) of 183 reporting countries in 2008, then decreased to 115 (60%) of 190 reporting countries in 2010 (Table 1).

During 2009–2010, a number of countries experienced large outbreaks, including Malawi (118,712 cases), Burkina Faso (54,118), Iraq (30,328), Bulgaria (22,004), South Africa (18,356), Zambia (15,754), Zimbabwe (9,696), Vietnam (9,391), Nigeria (8,491), Namibia (7,214), the Philippines (6,368), DRC (5,407), France (5,048), and Ethiopia (4,235). The outbreaks were primarily associated with low MCV1 coverage and, in Burkina Faso, DRC, Ethiopia, Nigeria, the Philippines, and Vietnam, with suboptimal or delayed SIAs. In areas with high reported coverage, outbreak investigations found that the number of susceptible persons had grown over several years among adolescents and adults who had missed vaccination and that reported national routine or SIA coverage masked subnational immunity gaps. In Bulgaria, Malawi, Zambia, and Zimbabwe, these gaps often were found in groups with limited access to health services or who were reluctant to vaccinate their children because of philosophical or religious objections.

Reported by

Robert T. Perry, MD, Alya J. Dabbagh, PhD, Marta Gacic-Dobo, Jodi L. Liu, MS, Emily A. Simons, MHS, David A. Featherstone, PhD, Peter M Strebel, MBChB, Jean-Marie Okwo-Bele, MD, Dept of Immunization, Vaccines, and Biologicals, World Health Organization, Geneva, Switzerland. Div of Viral Diseases, National Center for Immunization and Respiratory Diseases, James L. Goodson, MPH, Global Immunization Div, Center for Global Health, CDC. Corresponding contributor: James L. Goodson, j[email protected], 404-639-8170.

Editorial Note

After 8 years of decline, the number of reported measles cases remained stable in 2009 but increased in 2010. Continued decreases during 2009–2010 in WPR and SEAR contrasted with large outbreaks in EMR during 2009, in EUR during 2010, and in AFR during 2009–2010. In 2010, approximately 90% of cases were reported from AFR, EUR, and SEAR, and 40% of countries did not meet the annual incidence target of <5 cases per million population.

The increase in measles cases in 2010 occurred despite a steady rise in regional and global MCV1 coverage and high reported coverage through SIAs. Measles surveillance data and outbreak investigations provided critical information to identify gaps in population immunity, underserved populations, and program weaknesses, which led to corrective actions and refinements of vaccination strategies. In Iraq, Lesotho, Malawi, the Philippines, South Africa, and Zimbabwe the target age group for planned SIAs was widened beyond ages 9–59 months to include older groups affected by the outbreaks. In Zimbabwe, to build confidence in both routine and SIA vaccination among religious groups, specialized communication strategies were developed, the opening hours of vaccination services were customized to meet the community's needs, and government authorities advocated for vaccination with church leaders. In Ethiopia, a comprehensive review of previous SIA implementation and surveillance data led to a shift from using multiyear subnational SIAs to implementation of a national SIA conducted in two phases over 6 months and to the development of best practices used in the 2010 SIA. Surveillance data analyses and outbreak investigations should continue to be used to complement vaccination coverage monitoring to identify gaps in vaccination programs.

Interpretation of coverage and surveillance data is complicated by some limitations. Vaccination coverage can be biased by inaccurate estimates of target populations and reporting of doses delivered. Surveillance systems do not detect all measles cases because reporting is incomplete from communities and within health systems. Comparing annual measles case totals and incidence is difficult when completeness of reporting changes from year to year.

Measles elimination goals have been set by all WHO regions except SEAR, and elimination in the Region of the Americas has been achieved and maintained since 2002. In July 2010, a global technical consultation commissioned by WHO to evaluate the feasibility of measles eradication concluded that measles can and should be eradicated (8). The WHO Strategic Advisory Group of Experts on Immunization endorsed this conclusion in November 2010, adding that a target date should be based on measurable progress made toward existing objectives (9). In 2010, the world's two most populous countries made promising advances in measles control. China held the largest SIA in the world, vaccinating approximately 103 million children, and India began implementation of a 2-dose vaccination strategy.

Building on the previous WHO and UNICEF strategy, and recognizing the burden of congenital rubella syndrome and the availability of combination vaccines, the Measles Initiative has developed the 2012–2020 Global Measles and Rubella Strategic Plan.§ This plan aims to 1) achieve and maintain high levels of population immunity through high coverage with 2 doses of measles and rubella–containing vaccines, 2) establish effective surveillance to monitor disease and evaluate progress, 3) develop and maintain outbreak preparedness for rapid response and appropriate case management, 4) communicate and engage to build public confidence in and demand for vaccination, and 5) conduct research and development to support operations and improve vaccination and diagnostic tools.

To reverse the recent increase in global reported measles cases and to make further progress toward achieving 2015 objectives will require 1) overcoming declining political and financial commitments to measles control, 2) achieving uniform high coverage with 2 doses of MCV through routine services or SIAs, and 3) monitoring subnational MCV1 and MCV2 coverage data to guide the development of interventions to increase coverage. Reductions in measles mortality accounted for 23% of the estimated global decline in all-cause child mortality from 1990 to 2008 (10). This contribution to reaching United Nations' Millennium Development Goal 4 for reducing the mortality rate in children aged <5 years by 2015¶ is at risk unless the challenges to reaching uniform high coverage with 2 doses of MCV can be overcome.

References

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