How falling measles vaccination rates are putting millions of children at risk

How falling measles vaccination rates are putting millions of children at risk

As measles vaccination rates fall and children on zero doses rise, a new study calls for urgent action to prevent a resurgence of this deadly disease.

In a study recently published in the journalVaccinationsResearcher Pedro Plans-Rubió at the College of Physicians of Barcelona evaluated zero-, one- and two-dose vaccines in all World Health Organization (WHO) regions. They compared data from the WHO and United Nations UNICEF databases between 2019 and 2023 to assess whether current coverage of immunization is on track to meet the goals of the Immunization Agenda 2030 (IA2030).

Only 41.5% of WHO member countries currently have enough measles immunity to block virus transmission, with an R0 of 15, far behind what is needed to fully protect communities.

The study results showed several alarming trends: 1. Global two-dose vaccination coverage in 2023 decreased by 3.7% compared to 2019; 2. Single-dose vaccination coverage improved by 7.8% globally, but most measles vaccination coverage indicators show lower values ​​than those in 2019; and 3. Current vaccination coverage is not on track to achieve IA2030 agreements. These results highlight the need for public health policies and implementation to increase two-dose vaccination coverage worldwide.

Additionally, the study found that zero-dose measles vaccination coverage - which refers to children who did not receive doses - increased by 7.8% globally between 2019 and 2023, with a 24.9% increase in the African region. As of 2023, the number of zero-dose measles children was 40.6% higher than the level needed to halve zero-dose children by 2030, a key IA2030 target.

background

Measles, sometimes called “rubeola,” is a highly contagious airborne viral infection that causes high fever, cough, red eyes and skin rashes. It often affects children and was once fatal, although advances in clinical interventions have since reduced its severity.

Measles is an exclusive disease. Medical science has developed effective vaccines against the measles virus (genusMorbillivirus), which, in addition to intensive epidemiological surveillance, can contain its infectivity and stop its transmission. In this context, the Assembly's 73rd World Health Immunization Agenda (IA2030) committed to eliminating the disease from at least five World Health Organization (WHO) regions (out of six regions total) by 2030.

To achieve this agenda and effectively immunize individuals, two doses of vaccine (measles-containing vaccine [MCV]) are required. WHO has implemented the widespread distribution of the Measles-Mumps-Rubella (MMR) vaccine along with training on its administration for children between 12 and 15 months (first dose) and again between 3 and 15 years (second dose).

“High rates of routine measles vaccination can generate both individual measles protection and sufficient population immunity to block measles transmission in the community.”

Unfortunately, 2019 research designed to track global progress towards IA2030 targets shows that only 14.4% of countries had two-dose vaccination coverage of ≥95%. Of concern, the basic reproductive numbers (R0) of the African and Eastern Mediterranean regions were found to be ≥ 10, ≥ 11 and ≥ 13 in the Western Pacific regions. These R0 values ​​correspond to the required population immunity levels in the range of 90% (for R0 = 10) and 95% (for R0 = 20), and R0 is a metric that denotes the number of clinical cases that a single infection can cause within a community.

About the study

European countries achieved two-dose coverage of 92.5% - the closer to the 95% target than other regions - but it still fell short, highlighting uneven global progress.

The present study aims to update this information by assessing: 1. The global measles vaccination in WHO member nations (zero, one and two dose coverage); 2. Compare current variations in measles vaccination coverage to 2019 levels; and 3. Assess whether measles vaccination indicators are on track to meet IA2030 targets.

Study data were obtained from WHO and United Nations Children's Fund (Global and Regional) databases. This data is recorded annually in all WHO member nations in the six designated regions: Africa, the Americas, the Eastern Mediterranean, Europe, Southeast Asia and the Western Pacific.

When estimating the immunity levels of the HERD readings and similar measles vaccination indicators, it was assumed that one dose of vaccine provided 92% immunity to individuals, while two doses provided 95% immunity. Accordingly, the required immunity percentages were calculated based on R0 thresholds – for example, 93.3% of population immunity is required to block measles viruses with an R0 of 15.

"...traces from 2019 to 2030 to achieve a 50% reduction by 2030 were determined for three zero-dose measles coverage indicators: (1) Estimated number of children who did not receive the first dose of measles-containing vaccines (MCV1); (2) Mean of McV1-based zero-dose coverage; and (3) Mean dose coverage, that of one and two doses of one Masel dose rear cover were rejected.”

All statistical analyzes were performed in Microsoft Excel.

The number of zero-dose measles children (who did not receive the MCV1 vaccine) is estimated from 2019 and 2023, and a number of zero-dose children required from 2019 to 2030 to reach the IA 2030 target (9.65 million).

Study results

The Covid-19 pandemic disrupted measles immunization programs, leading to a 24.9% increase in zero-dose children in Africa and delaying recovery efforts in low-income regions.

Analysis results showed that on average only 85.2% and 77.1% of the region's children had received one or two doses of MCV vaccine. This represents a 3.7% reduction in two-dose vaccination coverage compared to 2019 and is significantly below the track's estimates for achieving the IA2030 targets. Notably, only the Western Pacific region met the 95.5% MCV requirement, while the European region achieved 92.5% coverage and all other regions were below 95%.

The dose-specific results showed that global zero-dose coverage was 65.3%, one-dose at 27.8% and two-dose at 6.9%, with Africa's zero-dose rate at 21.1% - far higher than other regions (less than 3%). These rates are more than 31% lower than the requirements of IA2030. The African region showed the lowest single-dose coverage at 48.1%, while the Western Pacific region had the highest coverage (93.2%). Only 17 WHO members (8.7%) were found to have two-dose vaccination coverage of 95% or greater.

Regarding herd immunity, the study found that only 41.5% of countries achieved sufficient immunity to stop transmission of measles viruses with R0 values ​​of 15 or lower, and no region achieved immunity sufficient to block viruses with R0 ≥ 19 or 20. Only the Western Pacific region and some countries in the European region reached levels in the European region.

Despite some regional variation - the Western Pacific region has shown modest improvements since 2019 - most areas, particularly Africa, showed deteriorations in vaccination coverage and herd immunity levels.

The study found that these trends were exacerbated by disruptions from the Covid-19 pandemic, which significantly impacted routine immunization programs and delayed recovery efforts.

Additionally, the paper highlighted limitations such as reliance on WHO/UNICEF data that may underrepresent gaps in certain populations and highlighted the need for serological surveys to assess real-world immunity.

Conclusions

One in five children in Africa have not received a dose of the measles vaccine, making it the region with the highest proportion of zero-dose children and the greatest risk of future epidemics.

The present study examines the effectiveness of Who-expensive anti-mice vaccination programs in its six regions between 2019 and 2023 (-3.7% for two-dose coverage), with only one region (Western Pacific) representing improvements over 2019 results. While single-dose coverage has increased by 7.8% globally, all metrics of measles vaccination coverage suggest that current efforts are not on pace to meet IA2030 targets.

This highlights the need for policy improvements and improved vaccination dissemination programs aimed at both education and successful two-dose vaccine administration to eliminate this disease in children from the human population.

The study also requires broader international collaboration and targeted efforts in regions such as Africa to close immunization gaps and build sustainable herd immunity.

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