Conflict is stalling child vaccination across the Sahel, WHO data show

Protracted conflict across the Sahel is leaving a growing share of children with no routine vaccines at all. An analysis of WHO Immunisation Data Portal figures across five Sahel countries found that in 2023, 22% of children in Mali and 16% in Chad were "zero-dose" — having received not a single routine childhood vaccine — with the highest share, 43%, in Sudan [s1]. Measles vaccine coverage sat below 90% in every one of those countries except Burkina Faso, the threshold below which outbreaks become hard to stop [s1].

What the analysis found

The study examined vaccination coverage and disease outbreaks in Burkina Faso, Chad, Mali, Niger and Sudan from 2019 to 2023, a period of deepening insecurity and shrinking humanitarian access across the region [s1]. As access contracted, the number of zero-dose and under-immunised children accumulated [s1]. Beyond the zero-dose figures, the analysis reported that nearly half of children in Sudan (49%) were under-immunised in 2023, along with 33% in Chad and 23% in Mali [s1].

The consequence shows up as outbreaks of the diseases those vaccines prevent. The analysis recorded circulating vaccine-derived poliovirus across the region, with Chad reporting 101 cases in 2020 alone and Niger reporting cases repeatedly over the period [s1]. It also noted significant polio outbreaks in Burkina Faso, Sudan and Mali in 2020, which the authors link in part to disruption during the COVID-19 pandemic overlapping with conflict [s1]. Circulating vaccine-derived poliovirus is itself a signature of low coverage: it emerges where too few children are immunised for the oral vaccine's weakened virus to die out.

Why conflict breaks immunisation specifically

Routine immunisation is unusually fragile in war because it depends on the two things conflict destroys first: a functioning cold chain and repeated, predictable contact between families and health workers. A child needs multiple visits on a schedule; displacement, insecurity and the closure or targeting of health facilities each break that schedule, and a missed early dose is the one least likely to be recovered. That is the pathway that turns insecurity into the zero-dose counts above — the same dynamic seen where conflict has stalled measles vaccination and left "zero-dose" children in Tigray, and a driver of the global stall in measles coverage that has let cases climb.

What might reach these children

A scoping review of strategies for reaching zero-dose children in fragile and conflict-affected settings across the WHO African Region offers a sobering companion finding: it identified only five qualifying studies published between 2018 and 2025, covering Nigeria, Cameroon, the Central African Republic, South Sudan and Ethiopia [s2]. The approaches that appeared to work relied on delivering vaccines through non-immunisation platforms, integrating services, securing negotiated access into contested areas, and using technology-enabled logistics to reach populations that fixed clinics cannot [s2]. But the review found the evidence base small and largely descriptive, with particular gaps in economic evidence and in assessing gender-related barriers [s2].

What the evidence cannot say

The Sahel analysis is a descriptive study built on aggregate WHO coverage figures and outbreak reports, not a causal evaluation; it documents that coverage fell as conflict intensified, but cannot isolate how much of the decline is attributable to conflict as opposed to the pandemic, funding shifts or reporting gaps in inaccessible areas [s1]. Coverage estimates in conflict zones are themselves uncertain, because the denominator — how many children live in an area a surveyor cannot reach — is often a guess. The scoping review, by design, maps what has been studied rather than measuring what works, and its five included studies do not cover the Sahel's core conflict countries directly [s2].

What to watch

The measurable questions are whether zero-dose counts in Mali, Chad and Niger stabilise or keep climbing as insecurity persists, and whether measles coverage — already below the 90% outbreak threshold across most of the belt [s1] — recovers before the next large outbreak. The strategies the review points to exist [s2]; what is missing is evidence that they can be delivered at the scale the zero-dose numbers now demand.

Sources

• Implications of conflict on vaccination in the Sahel region, BMJ Global Health, 30 January 2025
• Reaching zero-dose children in conflict-affected and fragile settings in the WHO African Region: a scoping review of strategies and evidence gaps, BMJ Public Health, 4 September 2026