By Richie Olaka
Despite unprecedented scientific progress, global immunization has yet to reach many of those who need it most. Each year, vaccines save an estimated 4 to 5 million lives, protecting children from diseases that once devastated entire communities. It is one of public health’s greatest success stories. Yet behind this progress lies a persistent and uncomfortable reality: millions of the world’s most vulnerable people remain unreached.
According to the World Health Organization, more than 14 million children received no routine vaccines at all in 2023 – so‑called “zero‑dose” children. The majority live in fragile, conflict‑affected, or hard‑to‑reach settings. If immunization is to fulfill its promise, success cannot be measured only by how many are reached, but by how many are still left out.
Today, the greatest barriers are no longer scientific but structural. Vaccines exist. Delivery does not always follow. Displaced populations, stateless communities, and the ultra‑poor are routinely missed. With more than 120 million people forcibly displaced worldwide, many living in protracted crises, health systems are often stretched beyond their design.
Conflict, in particular, exposes the limits of conventional immunization systems. Health workers flee, supply routes are disrupted, and entire regions become inaccessible. In such contexts, reaching children depends as much on negotiation as on logistics. During Côte d’Ivoire’s civil war, Rotary members entered rebel‑held territory to negotiate directly with armed groups, securing safe passage and protection for vaccination teams. For several days, children in areas otherwise cut off from services were able to receive life‑saving immunizations. Much of this experience has been shaped through decades of polio eradication work, which required reaching children in conflict‑affected, remote, and politically complex settings.
Even when services exist, they do not always reach those who need them most. Refugee settlements and displacement camps – such as those in northern Kenya – face chronic resource constraints and overstretched infrastructure. Children may begin a vaccination schedule only to miss follow‑up doses after being forced to move. Health records are lost. Supply chains falter. These gaps reflect not neglect, but the limits of systems built around stability rather than mobility.
For mobile populations, continuity is the central challenge. Immunization services are typically designed for settled communities, not for families on the move. Along the Pakistan–Afghanistan border, vaccination points established at transit crossings have helped ensure that children – and even adults – can receive vaccines as they travel. These approaches recognize a simple reality: if services do not move with people, people will remain unprotected.
Exclusion, however, is not only geographic – it is also social. Even in parts of Europe, entire communities remain outside the reach of routine immunization. Among Roma populations in Bulgaria and Romania, long‑standing mistrust of government programs has historically suppressed uptake. Targeted community engagement efforts by Rotary members have helped rebuild trust, bringing forward parents who had previously avoided immunization and demonstrating that confidence – not just access – is often the decisive factor.
Together, these experiences point to a broader truth: reaching those at the margins requires deliberate, adapted strategies. One‑size‑fits‑all systems, however effective for the majority, will continue to leave critical gaps.
Closing these gaps requires a shift in how immunization efforts are designed and measured. Inclusion must be treated as a core indicator of success. National health systems need to account explicitly for displaced and mobile populations rather than treating them as exceptions. In countries such as Kenya, efforts to integrate refugees into national health systems signal a move toward more sustainable and equitable approaches. Kenya recently launched the Building Health Resilient and Responsive Health Systems (BREHS) project which has a component of refugee inclusion into health systems.
Funding models must also reflect the realities of last‑mile delivery. Reaching the hardest to reach is more complex – and more costly. Yet the cost of uneven coverage is higher still. Recent outbreaks have shown that diseases thrive where protection is patchy. In an interconnected world, gaps in immunization anywhere pose risks everywhere.
There are proven models to build on. For decades, Rotary International and its partners have supported immunization efforts in some of the world’s most difficult environments, contributing to a more than 99.9% reduction in polio cases since 1988. This experience shows that even in fragile and conflict‑affected settings, sustained commitment, local engagement, and flexibility can deliver results.
It also underscores another essential insight: immunization does not happen in a vacuum. Where there is peace, health systems function; where conflict persists, they struggle to reach those most in need. Efforts to strengthen peace and resilience are therefore not separate from immunization – they enable it.
An immunization system is only as strong as the people it fails to reach. If we are serious about eradicating preventable diseases, we must design systems that prioritize those at the margins – not only those who are easiest to access. Because vaccines only work for every generation when they reach everyone.
The writer is a Rotary Peace Fellow and a specialist in forced displacement, working at the intersection of conflict, migration, and inclusive health systems.