Progress Toward Measles Mortality Reduction and Elimination --- Eastern Mediterranean Region, 1997--2007

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In 2005, the World Health Assembly set a goal of achieving a 90% reduction in global measles mortality by 2010, compared with levels in 2000 (1). Eight years earlier, in 1997, the 22 countries in the World Health Organization (WHO) Eastern Mediterranean Region (EMR)* had resolved to eliminate measles from their region by 2010.To reach these two goals, the WHO Regional Office for the Eastern Mediterranean developed a four-pronged strategy: 1) achieve and maintain >90% vaccination coverage of children with the first dose of measles-containing vaccine (MCV1) in every district of each country through routine immunization services, 2) achieve >90% vaccination coverage with the second dose of measles-containing vaccine (MCV2) in every district either through a routine 2-dose vaccination schedule or through supplementary immunization activities (SIAs),^§ 3) establish case-based surveillance with investigation and laboratory testing of all suspected cases of measles, and 4) provide optimal clinical-case management, including supplementation of diets with vitamin A (2). This report summarizes the progress made in the EMR during 1997--2007 toward reducing mortality from measles and eliminating measles from the region. Countries in the EMR reduced the number of measles-related deaths by approximately 75% from 2000 to 2007. However, large measles outbreaks continue to occur throughout the region, suggesting that much work remains to eliminate measles in the EMR.

Routine Immunization

MCV1 is administered at age 9 months in 12 (55%) of the 22 EMR countries and at age 10--15 months in the remaining 10 (45%). A total of 16 (73%) countries (accounting for 53% of the region's population) have a 2-dose MCV schedule (Table 1). Vaccination coverage with MCV1 and MCV2 is calculated annually for each country by dividing the total number of doses administered to children in the targeted age group by the census count of the number of children in that group. In addition, WHO and UNICEF estimate coverage of MCV1 annually for each country using reported coverage of MCV1 and survey results (3). For the region overall, estimated MCV1 coverage increased from 67% in 1990 to 83% in 2006 (Figure). In 19 countries, MCV1 coverage increased from 1997 to 2006 (Table 1). In 2006, 15 countries achieved >90% coverage of MCV1 nationally but did not achieve this coverage in all districts. In the 16 countries with a routine 2-dose schedule, eight reported MCV2 coverage >90% in 2006.

Supplementary Immunization Activities

During 1994--2007, approximately 188 million children in the EMR were vaccinated through SIAs. The majority of countries completed a catch-up SIA (4), with the exceptions of Morocco and Pakistan. In 2008, Morocco plans to conduct a catch-up SIA, and Pakistan plans to complete the final phase (phase 5) of the catch-up SIA begun in 2007 (Table 2). Kuwait, Saudi Arabia, and Syria each conducted a repeat catch-up SIA because timely follow-up SIAs were delayed and large measles outbreaks occurred. Egypt and Lebanon plan to conduct a repeat catch-up SIA in 2008. In 2007, follow-up SIAs were implemented in Afghanistan and Iraq; Sudan plans to complete a follow-up SIA in 2008.

Surveillance Activities

Since 2006, all countries in the region except Somalia, Morocco, and Pakistan have conducted case-based surveillance. Morocco and Pakistan have sentinel surveillance for measles with laboratory confirmation of cases identified at sentinel sites. In the countries with case-based surveillance systems, at least 80% of all cases of suspected measles are investigated using an individual case-reporting form. Confirmation of measles is made by clinical diagnosis, epidemiologic linking, or laboratory testing.^¶ In EMR countries with case-based surveillance, a blood specimen is sent to the laboratory for testing for measles immunoglobulin M (IgM) antibody in at least 80% of suspected measles cases.

An EMR regional measles laboratory network has been established, with a national laboratory in each country and regional reference laboratories in Oman and Tunisia. National laboratories perform confirmatory testing of suspected cases using an enzyme-linked immunosorbent assay to detect measles IgM antibody. In 2007, workers at nine of the 21 national laboratories were trained to perform measles virus isolation and polymerase chain reaction testing for viral detection. During 2003--2007, measles virus genotype D4 was the predominant strain of measles in eight of the 16 EMR countries where genotypes were identified, followed by B3 in six countries; however, genotype C2 was predominant in Morocco.

In 2006, WHO's Technical Advisory Group on Immunization in the Eastern Mediterranean Region recommended monitoring surveillance performance through standardized indicators and targets. These standards include ensuring that 1) at least two suspected cases of measles per 100,000 persons per year are detected and reported (to monitor the sensitivity of the surveillance system), 2) at least 80% of suspected measles cases are tested for measles IgM antibody (to monitor adequacy of testing), 3) at least 80% of specimens are received by a laboratory within 7 days of collection (to monitor timeliness of specimen transport), 4) at least 80% of specimens sent to the laboratory arrive in adequate condition (to monitor adequacy of specimen collection), and 5) at least 80% of laboratory test results are reported within 7 days (to monitor timely reporting).

In 2007, among the 18 reporting countries, regional targets for surveillance sensitivity were met by nine (50%) countries, adequacy of testing by 14 (78%) countries, timeliness of specimen transport by 11 (61%) countries, adequacy of specimen collection by 17 (94%) countries, and timeliness of laboratory reporting by 16 (89%) countries. Although countries in the region have made progress in strengthening case-based surveillance, as of December 2007, seven countries had not yet provided complete reports, and only one country had met all quality targets.

Monitoring Measles Mortality Reduction and Elimination

Before introduction of measles vaccination in the early 1980s, approximately 200,000 clinically diagnosed cases of measles were reported each year in EMR countries (5). After strengthening measles-control activities throughout the 1980s, reported cases declined 70% to approximately 60,000 in 1990, and the interval between measles epidemics increased from 2--4 years during 1980--1991 to 6 years during 1992--2004 (Figure). Overall, measles incidence was lowest in 2005 (29 cases per 1 million population); in 2006, incidence increased to 44 cases per 1 million population. In 2007, the reported number of cases of measles decreased, but those data are incomplete.** During 2006--2007, despite reported MCV1 coverage rates of >95%, a routine 2-dose schedule, and a catch-up SIA held during the preceding 8 years, measles outbreaks occurred in Egypt (2,315 cases), Lebanon (1,344), Qatar (495), Saudi Arabia (4,215), and Syria (868).

In the absence of a routine surveillance system for measles deaths, WHO uses a model to estimate measles mortality based on measles case counts (corrected for a certain level of underreporting), estimated case-fatality rates, and estimated vaccination coverage (6). In 2000, an estimated 96,000 measles deaths occurred in EMR countries compared with 23,000 in 2006, representing a 76% decrease (7).

Reported by: World Health Organization Regional Office for Eastern Mediterranean, Cairo, Egypt. Dept of Immunization, Vaccines, and Biologicals, World Health Organization, Geneva, Switzerland. Global Immunization Div, National Center for Immunization and Respiratory Diseases; J Goodson, EIS Officer, CDC.

Editorial Note:

EMR countries have made progress toward the global goal of achieving a 90% reduction in measles mortality by 2010. However, the regional goal of achieving a sustained measles incidence of less than one case per 1 million population might not be achieved by 2010 because implementation of the regional measles elimination strategy varies among countries. Attaining high coverage of MCV1 with routine vaccination and high MCV2 coverage with routine vaccination or SIAs will be critical to reaching both goals. Since adoption of the 2010 regional measles elimination goal in 1997, coverage of MCV1 increased from 70% to 82% in 2006, and measles incidence decreased by 70%, from 146 per 1 million population in 1998 to 44 per 1 million population in 2006. Nonetheless, periodic measles outbreaks in several countries with high coverage with MCV1, a routine 2-dose schedule, and recently implemented catch-up SIAs suggest that reported vaccination coverage might overestimate actual coverage. In-depth reviews of immunization services, including independent surveys of vaccination coverage and assessments of data quality, are needed to identify and address programmatic shortfalls in these countries.

Certain countries where the burden of measles remains high (notably Afghanistan, Iraq, Lebanon, Pakistan, Somalia, and Sudan) have encountered major challenges to establishing comprehensive measles-control activities because of competing public health priorities, natural disasters, and civil unrest. Nonetheless, a catch-up SIA was conducted in parts of Pakistan in 2007, and successful implementation of planned activities in Afghanistan, the state of Punjab in Pakistan, and Somalia in 2008 will accelerate progress toward the regional elimination and global mortality reduction goals. Despite these achievements, armed conflict and war present major challenges for measles-control activities in several areas of the EMR. Unpredictable mass population displacements and resettlements complicate the delivery of routine immunization services and planning of SIAs. Conducting SIAs in conflict settings and in areas with no local government requires establishing close linkages with the local community. A strategy of coordinating special "days of tranquility" for vaccination activities during SIAs has been employed in parts of Afghanistan, Pakistan, Somalia, and Sudan. However, vaccination teams and civilian populations remain at risk for violence during these SIAs, and coverage often is suboptimal. In 2007, the SIA in Somalia achieved the lowest coverage in areas with the most insecurity. Protracted armed conflicts over many years in parts of Sudan and Afghanistan create logistic challenges to the transportation and storage of vaccine during SIAs.

Strategies for implementing SIAs vary substantially among EMR countries (Table 2). SIA coverage data and implementation reports indicate that some countries did not achieve high coverage for all susceptible age cohorts; this might be related to the use of different SIA strategies (e.g., conducted over extended periods, targeted at different age groups, or covering fragmented areas). To prevent an accumulation of persons susceptible to measles and subsequent measles outbreaks, follow-up SIAs need to be implemented periodically until routine 2-dose measles coverage >90% with both MCV1 and MCV2 is achieved and maintained in every district.

WHO's Regional Office for the Eastern Mediterranean recommends that a routine dose of MCV2 be introduced into national immunization schedules after MCV1 coverage >80% has been achieved for at least 3 years. Receipt of 2 doses of MCV provides immunity to nearly all vaccinated children. Serologic studies indicate that 1 dose of MCV provides immunity in approximately 85% of children when administered at age 9 months and in >95% of children when administered at age >12 months (8). To further enhance the effectiveness of MCV1 on population immunity, EMR countries with low transmission and high coverage with MCV1 and MCV2 should consider revising the schedule for MCV1 so that it is administered at age >12 months.

Although advances have been made in EMR countries toward the goal of reducing global mortality, successful implementation of all components of the EMR elimination strategy will be needed to achieve the regional goal of measles elimination. Much work remains to be done to increase vaccination coverage with MCV1 and MCV2, to confirm the validity of reported vaccination coverage, and to ensure that routine immunization services and SIAs reach populations at high risk who reside in areas with poor access or civil strife.

References

* Afghanistan, Bahrain, Djibouti, Egypt, Iran, Iraq, Jordan, Kuwait, Lebanon, Libya, Morocco, Oman, Pakistan, Qatar, Saudi Arabia, Somalia, Sudan, Syria, Tunisia, United Arab Emirates, West Bank and Gaza Strip, and Yemen. For this report, the geographic regions West Bank and Gaza Strip are considered to constitute one country.

Measles elimination is defined as the absence of endemic measles cases for >12 months in the presence of adequate surveillance. One indicator of measles elimination is a sustained measles incidence of less than one case per 1 million population.

^§ Initial nationwide catch-up SIAs in EMR countries target all children aged 9 months--14 years and have the goal of eliminating susceptibility to measles in the general population. Periodic follow-up SIAs target all children born since the last SIA, including children who have already been vaccinated. Follow-up SIAs generally are conducted nationwide every 2--4 years and target children aged 9--59 months, with the goals of eliminating any measles susceptibility that has developed in recent birth cohorts and protecting children who did not respond to their first measles vaccination.

^¶ A clinically confirmed case is defined as illness in 1) any person with both fever and maculopapular rash plus cough, coryza, or conjunctivitis; or 2) any person in whom a clinician suspects measles infection. An epidemiologically confirmed case is defined as any illness meeting the clinical case definition for measles in a person who had direct contact with a person with laboratory-confirmed measles in which rash onset occurred 7--18 days before the epidemiologically confirmed case. Additional information available at http://www.emro.who.int/vpi/measles/media/pdf/measlesplan_2006_2010.pdf.

** Data on the number of reported measles cases for 2007 are incomplete for Djibouti, Egypt, Lebanon, Pakistan, and Somalia.

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