Progress and Challenges in the Global Fight Against Measles

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Measles, a highly contagious and vaccine-preventable disease, poses a significant public health threat, necessitating concerted global efforts to achieve and sustain elimination. Despite commitments from all six World Health Organization (WHO) regions to eradicate measles, no region has yet achieved and maintained this ambitious goal.

The Immunization Agenda 2030 (IA2030) underscores the urgency of measles elimination, positioning it as a pivotal indicator of the overall impact of immunization efforts. This comprehensive report delves into the progress made and challenges faced in the battle against measles from the year 2000 to 2022, shedding light on immunization activities, surveillance performance, reported measles cases, estimated case and death figures, and the current status of elimination verification.

Immunization Agenda 2030 and the Importance of Measles Elimination:

The IA2030, a global strategy aimed at promoting equitable access to vaccines, recognizes the critical role of measles elimination. The agenda emphasizes the need for robust measles surveillance systems to identify immunity gaps and underscores the goal of achieving equitable coverage, with 95% of children receiving two timely doses of the measles-containing vaccine (MCV). Measles, given its high infectivity, serves as a litmus test for the efficacy of routine immunization services, revealing weaknesses in the health system when outbreaks occur among unvaccinated children.

Surveillance and Immunization Activities:

Efficient surveillance systems are fundamental to monitoring and controlling measles outbreaks. The report evaluates the performance of global surveillance systems in identifying immunity gaps and tracking the spread of the virus. Additionally, it explores the diverse immunization activities undertaken globally to curb measles transmission, ranging from routine childhood vaccinations to supplementary immunization campaigns in high-risk areas.

Immunization Activities: The report highlights the dynamic trends in Measles-Containing Vaccine 1 (MCV1) coverage from 2000 to 2022. Despite a global increase from 72% to 86% in the first two decades, the COVID-19 pandemic caused a decline to 81% in 2021. In 2022, coverage rebounded to 83%, revealing variations across regions. Low-income countries experienced a decline from 71% to 66% during 2019–2022, emphasizing the disproportionate impact on vulnerable populations. While 34% of WHO countries achieved ≥95% MCV1 coverage in 2022, significant challenges persist in reaching the remaining children, with Nigeria, the Democratic Republic of the Congo, and Ethiopia leading in numbers of unvaccinated infants.

Measles-Containing Vaccine 2 (MCV2) coverage increased impressively from 17% in 2000 to 74% in 2022, attributed to widespread vaccine introductions. However, challenges persist, with 11 million children missing MCV2 through routine immunization in 2022. The expanding coverage of MCV2 across countries is notable, with a 98% increase from 2000 to 2022. The report underscores the critical role of supplementary immunization activities (SIAs), as approximately 115 million individuals received MCV through SIAs in 2022, complementing routine immunization efforts.

Surveillance Performance and Reported Measles Incidence: Measles surveillance plays a pivotal role in controlling outbreaks. The report outlines improvements in surveillance sensitivity, with 50% of reporting countries achieving the target in 2022, compared to 35% in 2021. However, challenges persist, and the discarded case rate might have risen due to increased testing during outbreaks. The number of specimens received for measles testing in 2022 increased significantly, indicating a robust surveillance system.

Reported measles cases exhibited a fluctuating pattern over the years. The significant decline from 853,479 cases in 2000 to 132,490 cases in 2016 showcased the efficacy of vaccination efforts. However, a resurgence occurred in 2019, with 837,922 reported cases, followed by a decrease to 123,171 cases in 2021. Alarmingly, in 2022, reported cases surged to 205,153, highlighting the impact of the COVID-19 pandemic on transmission rates.

Measles Cases and Mortality Estimates: Utilizing a revised model, the report estimates a substantial reduction in measles cases and deaths from 2000 to 2022. Vaccination efforts prevented an estimated 57 million deaths globally during this period. However, concerning trends emerged in 2022, with an 18% increase in estimated cases and a 43% rise in estimated deaths compared to 2021.

Regional Verification of Measles Elimination: Despite progress, no WHO region has achieved and sustained measles elimination. By the end of 2022, 83 countries (43% of all countries) had been verified to have achieved or maintained measles elimination. The report details the challenges faced by previously verified countries, including the reestablishment of endemic transmission in Brazil, Venezuela, and seven other countries since 2016.

Discussion: The decline in MCV coverage during the COVID-19 pandemic underscores the vulnerability of global immunization efforts. Disparities persist, with low-income countries experiencing the greatest declines. The report emphasizes the critical role of SIAs in closing immunity gaps and calls for accelerated recovery of immunization programs to reduce disease incidence. Despite improvements in surveillance, challenges remain, and the surge in reported measles cases in 2022 raises concerns about the impact of declining MCV coverage.

In conclusion, the report provides a comprehensive overview of the progress and challenges in the global fight against measles. It underscores the need for sustained efforts, increased investment, and innovative strategies to overcome existing hurdles and ultimately achieve the long-sought goal of global measles elimination.

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