Vaccine inequality persists despite a decade of global progress

A new World Health Organization (WHO) study reveals that despite notable progress, vaccine inequality continues to persist across income, education, and gender lines worldwide. The study evaluates how WHO’s decade-long efforts have advanced the global understanding and monitoring of immunization disparities, emphasizing that reaching every child with life-saving vaccines remains both a technical and moral challenge for global health systems.

The study, titled “Advancing Inequality Monitoring in Immunization: Reflecting on 10 Years of WHO Contributions”, published in Vaccines (2025), reviews WHO’s systematic work to strengthen inequality monitoring and integrate equity into immunization programs across low- and middle-income countries. The paper, produced by the Department of Data, Digital Health, Analytics, and AI at WHO, serves as a milestone reflection on how data-driven strategies have reshaped the pursuit of equitable vaccine coverage.

Measuring who gets left behind

Over the past ten years, WHO has developed a robust global framework for assessing inequality in immunization, shifting from aggregate national statistics to detailed, disaggregated data analysis. The study highlights that early in the last decade, vaccination success was measured mainly by national coverage rates, often masking deep disparities between population groups. WHO’s targeted interventions since then have sought to close this gap, ensuring that the “zero-dose” children, those who have never received a vaccine, are at the center of global health planning.

The authors outline how WHO, in collaboration with Gavi, UNICEF, and the Equity Reference Group for Immunization, built tools and systems to measure disparities by income level, maternal education, geographic region, gender, and maternal age. These data sources, primarily derived from Demographic and Health Surveys (DHS) and Multiple Indicator Cluster Surveys (MICS), enabled researchers to identify inequities and track progress at both national and subnational levels.

Two landmark reports, State of Inequality: Childhood Immunization (2016) and Explorations of Inequality: Childhood Immunization (2018), set the analytical foundation for the decade. The 2016 report revealed how wealth and maternal education remain powerful determinants of vaccination outcomes. By 2018, WHO introduced multidimensional frameworks that accounted for the compounding effects of multiple disadvantages. For example, children born to young, uneducated mothers living in poor, rural areas were found to be hundreds of times less likely to be fully vaccinated than children from wealthier, urban households headed by older, educated women.

This evidence underscored a critical reality: while global vaccine coverage has risen overall, systematic inequities continue to determine who benefits most. In some low-income countries, the difference in immunization rates between the richest and poorest households still exceeds 40 percentage points.

Building tools to turn data into action

In addition to identifying inequities, WHO has invested heavily in capacity building and knowledge dissemination to ensure that data inform policy. The study describes how WHO’s initiatives have transformed immunization monitoring from a technical exercise into a practical instrument for decision-making.

One of the major achievements highlighted is the creation of the Health Inequality Data Repository (HIDR), the world’s largest database of disaggregated health data, launched to give policymakers, researchers, and advocates easy access to inequality statistics. The repository complements the Health Equity Assessment Toolkit (HEAT), an interactive data visualization and analysis platform that allows countries to explore inequality patterns and design targeted interventions.

To support local implementation, WHO developed the Inequality Monitoring in Immunization: A Step-by-Step Manual (2019) and an eLearning course, guiding national health professionals through the full cycle of monitoring, defining inequality dimensions, obtaining and analyzing data, reporting findings, and translating evidence into policy.

These resources are now widely used in regional and national programs. WHO also established the Health Inequality Monitoring Network, a global community of practice that shares methodologies and supports country-led action. In addition, the organization has hosted multiple workshops and coordinated special editions of Vaccines focusing on immunization inequality, amplifying evidence-based approaches to equitable access.

The study credits WHO’s sustained technical support with enabling countries to institutionalize equity monitoring, embedding it within health information systems, strategic plans, and performance reviews. This institutional shift has redefined how governments evaluate progress, making fairness as central to success as overall coverage.

Persistent gaps and future challenges

While the study celebrates major achievements, it also delivers a sobering message: vaccine inequality remains a defining obstacle to universal immunization coverage. The authors document that economic, educational, and geographic gaps have narrowed in some regions but remain stubbornly wide in others, particularly across parts of sub-Saharan Africa and South Asia.

Emerging research shows that gender inequality is a critical but often overlooked factor. The WHO team found that women’s empowerment and decision-making autonomy directly correlate with childhood vaccination rates. Where women have limited social independence, vaccination coverage tends to lag behind. Addressing gender-related barriers, such as restricted mobility, limited access to health information, and low representation in community health decisions, is essential to closing the gap.

The study also highlights how new threats, including pandemic-related disruptions, misinformation, and vaccine hesitancy, have introduced additional layers of inequality. The COVID-19 pandemic reversed progress in many regions, with marginalized groups experiencing greater declines in routine immunization coverage. WHO’s ongoing work in tracking COVID-19 vaccine inequity revealed patterns that mirror traditional disparities, reinforcing the need for long-term monitoring mechanisms.

Looking forward, the authors outline several strategic priorities for the next decade:

• Scaling up disaggregated data collection to capture subnational and community-level inequities.
• Integrating geospatial and behavioral data into monitoring systems for greater precision.
• Bridging the gap between data and action, ensuring that monitoring results drive tangible policy reform.
• Expanding financial and political commitments to sustain equity-focused initiatives.
• Promoting innovations like UNICEF’s digital engagement programs and Gavi’s Zero-Dose Learning Hubs to reach unvaccinated populations.

These steps, the paper notes, are crucial to advancing the global goal of leaving no one behind, a principle key to the Immunization Agenda 2030.

The upshot is that WHO’s decade-long investment in inequality monitoring has mainstreamed equity as a core principle of immunization strategy. Tools like HEAT and HIDR have become foundational assets for health ministries and international partners, helping translate data into policies that directly target the most vulnerable populations.

Yet, the authors warn that the next stage of progress depends on sustained collaboration between global institutions, governments, and communities. Data systems alone cannot close inequality gaps without political will, local engagement, and targeted funding.