Childhood immunization: who is catching up, who is falling behind

A measles vaccine costs less than one dollar. An outbreak, by contrast, is measured in hospital admissions, in children's deaths and in lost trust in the health system. In 2024, the World Health Organization African Region broadly recovered its pre-pandemic immunization levels, with the third dose of DTP climbing back to around 76 % across this continental region. But this average masks a two-speed zone: on the West African map alone, solid catch-up performers (Ghana reaches 95 %, Senegal 91 %) sit alongside worrying laggards, with Benin collapsing to 44 % measles coverage, one of the lowest rates in the region and one of the ten lowest in the world. The gap between the two is no geographic inevitability: it is the product of decisions, of funding and of measurement systems. A data-driven demonstration.

A reassuring regional average, a two-speed reality

The continental figure is encouraging: across the WHO African Region, DTP3 coverage, the benchmark indicator of a routine immunization programme's strength, rose to around 76 % in 2024, erasing the setback caused by the pandemic. The movement is global: in low-income countries, DTP3 coverage gained one point to reach 82 %, and the number of children having received no dose fell by about 500,000 over a year, to 10.2 million. But within West Africa, the average conceals gaps of nearly thirty points between countries. At the top, Ghana (95 %) and Senegal (91 %), tied with Burkina Faso (91 %), are consolidating mature systems. In the middle, Niger (86 %), Mali (82 %) and Côte d'Ivoire (77 %) are holding steady. At the bottom, Nigeria (67 %) and above all Benin (63 %) carry a structural lag that weighs on the whole zone.

Thirty points of gap between two neighbouring countries, subject to the same climatic constraints and the same regional supply chains, is itself a piece of information. It signals that immunization coverage depends less on income level or environment than on the quality of management: the political priority given to routine services, the regularity of funding, the density of the facility network and, increasingly, the ability to find the missing children. That is precisely what the rest of this analysis seeks to isolate.

Benin's measles decline, an alarm signal

While DTP3 measures the strength of routine immunization, measles coverage (first dose, MCV1) measures the ability to protect against one of the most contagious diseases known, for which the 95 % threshold is needed to halt transmission. On this indicator, Benin's decline becomes critical: just 44 % coverage in 2024, down 8 points in a single year (52 % in 2023). This level places Benin, tied with Papua New Guinea (also 44 %), among the world's ten worst performers on the first measles dose according to the 2024 revision of the WHO/UNICEF estimates, just ahead of the Central African Republic and Yemen (41 % each). Nigeria, at 57 %, also remains well below the epidemic threshold. At the other end, Ghana (90 %), Burkina Faso (88 %) and Senegal (87 %) protect their cohorts, while Côte d'Ivoire (75 %) and Mali (72 %) hold an intermediate position.

At 44 % measles coverage in 2024, down from 52 % a year earlier, Benin ranks among the world's ten worst performers on the first dose, a decline that calls for an immediate response.

Catch-up is possible: what the comparative trajectory shows

Falling behind is not a regional inevitability, and recent history proves it. Comparing Mali's DTP3 trajectory with Benin's is instructive. In 2023, the two countries started from different but not incomparable positions. In 2024, Mali recorded one of the region's strongest gains, adding 7 points (from 75 % to 82 %), and this despite a context of humanitarian and security fragility far heavier than Benin's. Over the same period, Benin stayed stuck at 63 %. The lesson is clear: a difficult environment does not, on its own, explain low coverage. Where Mali maintained its campaign and outreach effort, Benin let its measles coverage slide by 8 points in twelve months.

This contrast has methodological value for decision-makers: it invites them to stop reasoning by determinism (a country supposedly condemned by its geography or income) and to look at what, in management, moves the curve. The levers identified in Mali, regular follow-up campaigns, outreach strategies toward isolated areas, community mobilization, are transferable. But they must be triggered in the right place, which requires knowing where the unvaccinated children are.

The mechanics of falling behind: breaking down the why

Why is a child not vaccinated? Regional surveillance data offer a useful breakdown. Analysis of notified measles cases in West Africa in 2024-2025 shows that 85 % of patients were either unvaccinated (57 %) or of unknown vaccination status (28 %). In other words, the vast majority of cases occur among children the system has never reached or has never managed to track. Unknown status is no detail: it signals a recording and traceability deficit, which prevents targeting catch-up actions. This dual cause, a coverage failure and a measurement failure, structures the whole response that is needed.

To these two causes is added a documented gap between reported and actual coverage. During the 2024 measles-rubella follow-up campaigns, administrative coverage exceeded 95 % in most countries, but post-campaign surveys revealed gaps: only Senegal (93 %) and Guinea-Bissau (94 %) achieved high verified coverage, and no country actually crossed the 95 % national threshold. Steering on administrative figures alone therefore sustains an illusion of safety. The main mechanics of falling behind can thus be summarized as follows.

• Children never reached: 57 % of notified measles cases involve unvaccinated children, often in specific geographic pockets.
• A traceability deficit: 28 % of cases are of unknown vaccination status, a sign that name-based registration and cohort follow-up are lacking.
• A gap between reported and actual: administrative coverage exceeds 95 % while survey-verified coverage stays below the threshold, creating a false sense of protection.
• The missing second dose: several countries, including Benin, have not fully integrated the second measles dose (MCV2) into routine schedules, leaving cohorts insufficiently protected.

Zero-dose: the absolute burden concentrates in Nigeria

Percentages do not tell the whole story: we must think in numbers of children. Globally, about 14.3 million infants received no dose in 2024, and nearly half of the 10.2 million zero-dose children in low-income countries live in just five countries: Nigeria, DR Congo, India, Pakistan and Ethiopia. Nigeria bears the heaviest absolute burden, not only in the region but in the world, with on the order of 2.1 million children having received no dose of DTP. Niger would count around 350,000, Benin nearly 220,000 and Mali about 157,000 (2021 estimate). Across West and Central Africa, and according to the 2024 revision of the WHO/UNICEF estimates analysed by Mwale et al. (Vaccine journal), the subregion alone concentrated 7.2 million children deprived of a first measles dose, or 46.2 % of the global total of children unvaccinated against the disease.

Framing by volume changes prioritization. A populous country with average coverage, such as Nigeria, can concentrate more unprotected children than a small country with very low coverage. The optimal regional strategy is therefore not uniform: it must combine a mass response where the volume is enormous (Nigeria) and a rapid-recovery response where the rate is collapsing (Benin on measles).

The cost of inaction: what eroding coverage really costs

Letting coverage slide has a price, and it materializes quickly. In 2025, the number of districts hit by a measles outbreak in West Africa rose to 383 in 13 countries, against 64 districts in 7 countries in 2024, a sixfold increase in a single year. Globally, measles caused about 11 million infections in 2024, exceeding the pre-pandemic level by nearly 800,000 cases. The mechanism is relentless: below the 95 % threshold, every insufficiently vaccinated cohort feeds the next epidemic, which strikes the youngest first. Children under five accounted for the majority of cases, but a third already involved children aged 5 to 14, those cohorts that had escaped vaccination in previous years.

In one year, the districts hit by a measles outbreak in West Africa rose from 64 in 7 countries to 383 in 13 countries: the cost of inaction is measured in weeks.

Conversely, investing in immunization shows one of the best returns in public health. According to the Decade of Vaccine Economics programme, every dollar invested in vaccination against ten pathogens in low- and middle-income countries returns about 21 dollars under the cost-of-illness approach, and up to 54 dollars under the value-of-a-statistical-life approach. The measles vaccine alone concentrates a large share of that return. Forgoing the protection of a cohort therefore saves nothing: it shifts an avoidable, and far heavier, expense onto hospitals and families.

What national averages hide, and why the field changes the decision

Behind every national rate lies a geography of inequality. Several countries in the region, including Guinea, Mali and Nigeria, show some of the largest immunization equity gaps, with disparities that can exceed twenty percentage points between the wealthiest and poorest households. In Benin, the divide is first and foremost territorial: according to estimates, a majority of children live in rural areas, where zero-dose rates are markedly higher than in cities, particularly in the north of the country. As long as programmes reason in national averages, they remain blind to the pockets of population that concentrate most of the risk. A national coverage of 63 % can hide communes at 90 % and others at 30 %, and it is on the latter that epidemics ignite.

This is where fine-grained measurement becomes an act of management, not a mere statistical exercise. The finding that 28 % of measles cases are of unknown vaccination status, and that administrative coverage overstates reality by several points, points to the same need: a disaggregated, name-based, geolocated monitoring system. Knowing that a country reports 44 % does not say where to act. Knowing that a given northern commune reports 30 % zero-dose, that cold-chain breaks recur there and that birth registration is patchy, points to an immediate operational decision. The value of data lies not in its decimal precision, but in its ability to name the next child to reach.

This is the conviction that structures CRAD's approach to public health: data has value only if it is disaggregated down to the level where decisions are made, the health facility, the commune, the wealth quintile. Measuring finely, cross-referencing immunization coverage, birth registration and geographic access, and delivering the whole in an actionable form, turns a passive national rate into a roadmap. At the regional scale, the Big Catch-Up initiative illustrates what a targeted approach can produce: between 2023 and 2025, it reached about 12.3 million zero-dose children across 36 countries, including 2 million in Nigeria alone on the first DTP dose. Targeting, not the average, drives performance.

Gender and territorial equity, the condition for the final stretch

The last fraction of unvaccinated children is also the hardest to reach, and the most marked by inequality. The wealth gaps above twenty points, observed in Guinea, Mali and Nigeria, are often compounded by gender barriers: the mother's level of education, decision-making autonomy within the household, distance to facilities. A child living in a poor rural household, in a remote region, whose mother has little schooling, accumulates the probabilities of being zero-dose. Closing the regional gap will therefore not be decided on the average, but on these precise profiles. It is a further reason to steer by subgroup: the target is not a country, it is a combination of territory, income and gender.

Mali, a real but fragile catch-up

Mali's case deserves close monitoring, because it carries a double lesson. On one hand, it proves that catch-up is possible even in a constrained environment: +7 points of DTP3 in a year amid humanitarian and security fragility. On the other, it remains fragile: the volume of zero-dose children and the scale of equity gaps are a reminder that coverage gains can reverse quickly if the logistical and financial effort weakens. The lesson for the region is that progress is never secured. Without sustained funding and a measurement system able to flag a decline before it turns into an epidemic, the Mali of 2024 could meet the fate of the Benin of 2024.

← All insights