Despite substantial advances toward measles elimination during the past two decades, progress seems to have stalled. In 2010, the World Health Assembly (WHA) set a goal of achieving three milestones related to measles control by 2015 (see table).
From 2000 to 2018, the World Health Organization (WHO) has been tracking progress toward measles elimination in the six WHO regions, with a focus on vaccination coverage, disease incidence and disease mortality. Overall, worldwide measles disease burden and disease mortality have decreased substantially during this 18-year period, and a higher percentage of people have been protected by receiving measles-containing vaccines. However, the 2015 global milestones set by the WHA have not been met, and significant setbacks have occurred in recent years, resulting in an increasing incidence of measles disease worldwide.
Milestone 1: Increase coverage with first dose of measles-containing vaccine (MCV1) among children 1 year of age
The first WHA milestone was to increase the MCV1 coverage of children to 90% or higher in every country. Also, within countries, a goal was set to achieve at least 80% coverage in each district.
In 2000, only 45% of countries had 90% or higher MCV1 coverage. The lowest coverage was observed in the African WHO region (9% of countries met the goal) and the highest coverage was observed in the Americas, with 63% of countries achieving 90% or higher coverage.
In 2018, the overall number for all regions increased to 61%. The largest increases in coverage were observed in the African region (from 9% to 30%) and the Southeast Asia region (from 30% to 82%). There was no change in MCV1 coverage in the Eastern Mediterranean region, and little change occurred in the Americas. As of 2018, none of the WHO regions had achieved 90% or higher coverage in all countries.
Milestone 2: Reduce global measles incidence
The second goal of the WHA aimed to reduce global measles incidence to less than five cases per 1 million people. Although this goal was not met, the incidence decreased from 145 to 49 cases per million, a decrease of 66%.
While the total number of annually reported measles cases decreased from 853,479 in 2000 to 353,236 in 2018, there has been a 167% increase in cases since 2016 (see figure). Furthermore, each of the six WHO regions has seen an increase in cases during the past two years, except the Western Pacific region. The largest proportional increase in reported cases since 2016 has occurred in the Americas at a 16,732% increase. However, the overall contribution to global reported cases from the Americas remains relatively low.
The cause of this sharp global uptick in cases likely is multifactorial. The majority of these cases seem to be related to large outbreaks in a few countries. It also is thought that there may be “immunity gaps” where specific populations are inadequately protected, leading to ongoing transmission and outbreaks. Another suspected factor contributing to these outbreaks is increased travel by both infected people and by susceptible, unvaccinated people.
Milestone 3: Reduce global measles mortality
The third WHA milestone addressed mortality associated with measles. Since 2010, measles-related mortality has decreased by 73%. Despite failing to achieve the goal of 95% reduction, measles vaccination has resulted in an estimated 23.2 million averted deaths between 2000 and 2018.
In summary, monumental efforts have been made to reduce the burden of measles on a global scale. Subsequently, the number of cases and deaths from measles have declined in the past two decades. However, these trends have not continued in the past two years, and progress toward measles elimination seems to have regressed since 2016. It is thought that the increasing incidence and mortality likely will be reversible by strengthening immunization programs, identifying immunity gaps, vaccinating travelers adequately and improving surveillance efforts.
Which of the following trends has (have) been observed in measles globally since 2000?
A. Decreased number of deaths
B. Increased incidence
C. Decreased vaccination coverage
D. All of the above
Dr. Haston is a post-graduate training fellow in pediatric infectious diseases at Emory University School of Medicine and Children’s Healthcare of Atlanta (CHOA). Dr. Pickering is adjunct professor of pediatrics at Emory University School of Medicine and CHOA.