Vaccines have existed since the last century, proving to be effective, safe, and affordable. Yet, as of 2024, 14.3 million children had not received any vaccine doses—these are known as zero-dose children (ZDC). The world set a goal to reduce ZDC by 25% by 2025, but this target was not met.
If the effectiveness of vaccines is unquestionable, then we must ask: why, in 2026, do so many children still lack access? This issue is not about the science behind vaccines; instead, it reflects our collective inability to provide essential health services to those who need them most—a problem rooted in the shortcomings of Universal Health Coverage (UHC).
Immunisation: the ultimate test for UHC on all fronts
UHC is shaped by three core questions: Who receives coverage? What services are included? And how much financial protection do people actually have? When health systems are weak, immunisation typically falls short across all these aspects. Zero-dose children (ZDC) are left out of service coverage. Vaccines may be missing or inadequately funded in essential benefits packages. As a result, families whose children aren't vaccinated remain financially at risk from diseases that vaccines could prevent.
Immunisation rates have long served as a stand-in for assessing overall health system performance—not arbitrarily, but because ensuring every child receives three vaccine doses demands a fully functioning system: robust financing, reliable supply chains, skilled personnel, and effective community outreach. When this system works, other health services tend to thrive as well. Conversely, when these critical components fail, it triggers a chain reaction that disrupts other essential health services.
The financing evidence is clear
Particularly in low-income countries, vaccination coverage correlates closely with government health expenditures rather than GDP, total health spending, or donor aid. Countries spending more on immunisation from government sources have achieved approximately 94% DTP3 coverage, whereas those who spend less have plateaued at about 72%. This disparity underscores the importance of political prioritisation instead of economic status. The COVID-19 pandemic further emphasised that public financing commitment not only drives coverage but also strengthens system resilience.
Gavi, the Vaccine Alliance, has had a significant impact on immunisation efforts. However, countries graduating from Gavi support are expected to finance vaccines independently through government health budgets, yet many remain unprepared for this transition. It is projected that approximately 40 countries will continue to be dependent on Gavi as the primary source of financing immunisation until 2040, indicating ongoing dependence on external financing for immunisation. A 2025 microsimulation study estimated that vaccines in Gavi-eligible countries prevented nearly 200 million cases of catastrophic health expenditure, with almost half of these benefits accruing to the poorest and most marginalised populations. Consequently, when immunisation financing falters, disadvantaged families face both denial of healthcare services and significant financial risk.
The equity issue is a matter of financial strategy
Unvaccinated and under-vaccinated children are concentrated in marginalised groups—typically those already lacking access to general healthcare, such as households with the lowest incomes, people in conflict zones, or those living in remote areas. The main barrier to reaching these children isn't usually logistics but rather equity, which ties directly back to government funding decisions. Immunisation offers benefits to entire populations through herd immunity, making it a public good that is typically funded by governments. Bridging the equity gap requires prioritising domestic budgets, ensuring steady multi-year funding commitments, and implementing fiscal policies that reach local systems, especially where immunisation rates are low. This must be supported by strong mechanisms for procuring affordable, reliable vaccine supplies, like pooled procurement systems.
Partnerships for immunisation
The GSK and Save the Children partnership, now in its second decade, operates in Ethiopia and Nigeria—both with high numbers of zero-dose and under-immunised children. Through the BOOST program, it aims to improve immunisation by supporting service delivery, increasing demand, and strengthening policies and financing, working closely with governments. The partnership has helped to reach over 700,000 children with immunisations and demonstrates the importance of collaborative and innovative approaches.
A necessary reframing
Communities with high zero-dose rates face not only challenges in immunisation, but also broader issues of health system exclusion. Zero-dose children serve as key indicators for populations who remain underserved. Areas with the highest prevalence of zero-dose children often experience the greatest barriers to accessing a range of health services. Addressing this issue should be considered integral to achieving UHC, rather than a separate objective.
UHC requires that every child has equitable access to necessary health services without financial burden. Immunisation is central to this goal and serves as a critical measure of success. At present, shortcomings in reaching all children are not due to vaccine efficacy, but rather the limitations in existing systems for financing and delivering immunisation services.
