Perspective

The Eliminate Yellow Fever Epidemics (EYE) Strategy was developed following the 2016 outbreaks in Angola and the Democratic Republic of the Congo, which exposed the potential for urban amplification, vaccine shortages and international spread of yellow fever[1]. Its three strategic objectives: to protect at-risk populations, prevent international spread and rapidly contain outbreaks; have guided investments in preventive vaccination, routine immunization, vaccine supply, laboratory capacity, surveillance and outbreak response[1,2].

These investments have produced substantial gains. By the end of 2023, approximately 377 million people in high-risk African countries had been vaccinated, vaccine supply for Gavi-eligible countries had increased considerably, and a six-million-dose global emergency stockpile had been maintained [3]. Regional laboratory capacity also expanded, with diagnostic capacity established across most high-risk countries [3]. More recent EYE implementation tools continue to emphasize population immunity, case detection and investigation, outbreak response and prevention of international spread [4].

Yet these achievements coexist with persistent transmission. Yellow fever cases and outbreaks continued across Africa in 2024 and 2025,[5] and transmission remained active in 2026. WHO reported confirmed cases in Burkina Faso, Cameroon and the Central African Republic during the first five months of 2026, with suspected cases under investigation in several other African countries[6]. Average yellow fever vaccination coverage across the African Region was only about 65% in 2024 [6].

The central question at the end of EYE is therefore not whether the strategy generated progress – it clearly did – but whether the architecture that delivered that progress is sufficient for the risk environment that now exists. We argue that the post-2026 agenda should evolve from a largely campaign-, detection- and response-oriented elimination programme toward an adaptive preparedness architecture that continuously manages population immunity, ecological risk, human mobility, surveillance and health-system resilience.

From campaign success to sustained population immunity
Vaccination remains the most effective intervention against yellow fever, and preventive mass vaccination campaigns were indispensable to EYE. However, people reached through campaigns should not be equated automatically with durable population protection. At mid-term, only 22% of African high-risk countries had achieved at least 80% routine yellow fever vaccination coverage, while only 43% of assessed high-risk areas achieved at least 80% coverage through completed campaigns [2]. By 2022, only four of 27 high-risk African countries had routine yellow fever vaccination coverage of at least 80%[3].

These gaps indicate a necessary transition from periodic campaign achievement to continuous management of population immunity. Importantly, WHO concluded that suboptimal yellow fever coverage increasingly reflected weaknesses in routine immunization and broader health-system performance rather than problems unique to yellow fever vaccination [2]. National evidence reinforces the heterogeneity hidden by aggregate coverage. Analysis of Nigerian surveillance data identified age, occupation, recent travel, ecological setting and uncertain vaccination status among factors associated with yellow fever virus positivity[7]. A recent systematic review similarly identified vaccination gaps, limited healthcare access among mobile populations, weak surveillance and urbanization among recurring drivers of yellow fever re-emergence in Africa[8].

Post-2026 planning should therefore connect routine immunization, catch-up vaccination, subnational immunity-gap analysis and targeted strategies for zero-dose, mobile and hard-to-reach populations. Preventive campaigns should remain available where needed, but success should increasingly mean sustained immunity in populations at greatest risk rather than cumulative numbers vaccinated. Sustaining population immunity will also require attention to vaccine confidence and acceptance. Recent evidence from Ghanaian nomadic communities identified insufficient information, concerns about vaccine safety and side effects, fear of allergic reactions, distrust of health services and doubts about vaccine effectiveness among reported barriers or concerns surrounding yellow fever vaccination [9]. Post-2026 strategies should therefore complement vaccine delivery with context-specific risk communication and community engagement, particularly among populations with persistent immunity gaps.

From static risk classification to dynamic risk intelligence
EYE was designed as a risk-based strategy, but yellow fever risk is increasingly dynamic. The WHO mid-term evaluation noted that the countries prioritized by EYE remained largely unchanged during the first six years despite changing vector distributions, climate conditions, population movement and outbreak patterns[2]. It consequently recommended more frequent subnational risk assessment and reconsideration of countries classified outside the highest-risk group.

Recent African evidence supports this shift. Climatic and ecological characteristics were independently associated with yellow fever virus positivity in Nigeria, while occupational exposure and recent travel were also relevant[7]. Climate-sensitive modelling has demonstrated that future yellow fever burden is likely to change unevenly across Africa as temperature and rainfall alter transmission suitability[10]. The continuing expansion of Aedes mosquitoes, rapid urbanization, land-use change, insecurity and population displacement further challenge the assumption that future risk will reproduce historical patterns [6,8].

Population mobility also requires more sophisticated treatment than formal border controls alone. Population-connectivity mapping at the Tanzania-Kenya and Tanzania-Uganda interfaces identified networks associated with trade, pastoralism, fishing, tourism, health-seeking, agriculture, education and cross-border marriage, and these findings were subsequently used to strengthen surveillance and vaccination planning[11].

We therefore propose a shift toward dynamic risk intelligence. Under this proposed post-EYE framework, vaccination coverage and reported cases would be considered alongside vector distribution, rainfall and temperature, land-use change, mobility, urban expansion, conflict and health-system capacity. Rather than assuming that these indicators can reliably predict outbreaks, their integration could support more frequent subnational risk assessment and help identify settings in which vulnerability may be increasing. Translating this risk intelligence into timely action, however, depends on surveillance systems capable of detecting and investigating emerging signals.

From yellow fever surveillance to integrated epidemic intelligence
EYE made important investments in diagnostics and surveillance, but persistent bottlenecks remain between clinical suspicion, specimen collection, transport, confirmation and action [2]. Recent evidence from Ghana illustrates the distinction between having a surveillance system and having a sufficiently responsive one. Between 2018 and 2022, 93% of suspected yellow fever specimens were collected within 14 days of symptom onset, yet only 41% reached the national reference laboratory within three days of collection [12]. Geographic differences in transport times were substantial, particularly for more remote areas.

Yellow fever surveillance after 2026 should therefore evolve beyond strengthening individual stages of pathogen-specific surveillance toward integrated epidemic intelligence. This direction is increasingly consistent with the WHO Global Arbovirus Initiative, which emphasizes risk anticipation, epidemic prevention, vector control, preparedness, innovation and coordinated action across arboviruses [13]. WHO’s global assessment of arbovirus surveillance capacity also found that many resource-constrained settings lack systems capable of reliably detecting transmission even where competent vectors are present [14].

This is particularly relevant because yellow fever shares vectors, ecological drivers and overlapping clinical presentations with other arboviruses [13,15].  Recent analyses argue that yellow fever is increasingly situated within a wider arbovirus-risk landscape shaped by climate change, urbanization and mobility [16]. WHO has similarly moved toward integrated clinical guidance for yellow fever, dengue, chikungunya and Zika [15]. Variation in the clinical presentation and severity of yellow fever also has implications for surveillance and outbreak detection. Early illness may be clinically non-specific, while a proportion of patients progress to severe disease characterized by jaundice, organ dysfunction and haemorrhagic manifestations. Clinical overlap with other febrile and arboviral illnesses may complicate recognition, particularly where access to laboratory confirmation is limited [15].  Post-EYE strategies should therefore strengthen frontline clinical recognition, differential diagnosis and timely referral for laboratory investigation as part of integrated surveillance.

For Africa, this suggests linking human surveillance with entomological, environmental and, where feasible, non-human-primate surveillance. A proposed One Health model for Uganda illustrates how human, animal and environmental information can be brought together for yellow fever prevention,[17] while experience from non-human-primate surveillance demonstrates the potential of epizootic signals to provide earlier warning of human risk [18]. Such integrated intelligence would be most valuable if it informs action before human transmission escalates.

From reactive containment to anticipatory preparedness
Rapid containment was appropriately central to EYE. However, its experience also demonstrates the limitations of relying on detection of human transmission as the primary trigger for mobilization. The EYE monitoring framework targeted initiation of reactive vaccination campaigns within 86 days of symptom onset in the first case, yet only half of outbreaks met this benchmark in 2021[19].  Delays occurred across case detection, specimen transport, diagnostic confirmation and administrative processes for initiating reactive vaccination campaigns [19].

The post-2026 objective should therefore extend beyond rapid response toward anticipatory preparedness. WHO’s 2026 risk assessment already recognizes the interaction among rainfall, temperature, mosquito ecology, population immunity and mobility in determining current risk [6]. Climate modelling and population-connectivity information offer opportunities to identify changes in vulnerability that can inform anticipatory preparedness [10,11].

Anticipatory preparedness could use such signals to trigger subnational risk assessment, targeted vaccination, intensified vector surveillance, community engagement and readiness planning [20]. This would not replace outbreak response; rather, it would reduce the frequency with which emergency response becomes the first substantial intervention. Sustaining such preparedness, however, requires these capacities to be institutionalized and financed within national health systems.

From an externally supported programme to resilient national architecture
The sustainability question may be the most consequential challenge after 2026. The EYE mid-term evaluation found no substantial framework for sustaining achievements beyond the strategy period, continued dependence on external financing and limited national resource-mobilization planning [2]. The African regional progress report subsequently continued to identify financing constraints, weak health systems and limited country ownership among major implementation challenges [3].

Recent commentary has therefore cautioned against allowing the conclusion of EYE to create a financing and coordination vacuum and has advocated greater integration of yellow fever activities into primary health care, routine immunization, laboratory networks and domestic health financing [21]. We agree with that direction but argue that integration should go further: it should become the organizing principle of the successor architecture rather than a mechanism for preserving a vertical yellow fever programme.

Routine vaccination should sit within national immunization systems; diagnostic capacity within integrated laboratory networks; yellow fever surveillance within broader epidemic and arbovirus intelligence; mobility within cross-border preparedness; and vector and ecological surveillance within multisectoral One Health structures. This direction is already compatible with the Global Arbovirus Initiative and Immunization Agenda 2030 and provides a pathway for using limited resources across overlapping epidemic threats [4,13].

Equity should similarly become measurable rather than aspirational. The EYE evaluation found limited explicit attention to gender, equity and human rights in its strategy and monitoring framework and no systematic requirement for disaggregated indicators among groups at elevated risk [2]. The successor framework should therefore routinely identify who remains unprotected, where immunity gaps persist, why populations are repeatedly missed and whether emerging environmental or social changes are concentrating risk in particular communities.

Rethinking what counts as success
A redesigned architecture also requires a different measurement framework. The EYE experience showed the value of measurable targets but also exposed limitations arising from missing baselines, ambitious targets, limited disaggregation and inconsistent trend reporting [2]. Post 2026 monitoring should therefore balance programme outputs with measures of resilience.

Vaccination indicators should capture not only doses delivered but sustained subnational immunity and persistent zero-dose pockets. Surveillance indicators should measure the entire pathway from community detection to laboratory confirmation and action. Risk-assessment indicators should document how frequently epidemiological, climatic, vector and mobility data alter programme decisions. Equity indicators should identify population groups repeatedly missed by vaccination and surveillance. Sustainability indicators should track domestic financing, workforce capacity and integration of yellow fever functions into existing national systems. The purpose of such measurement would not be to create a larger dashboard. It would be to ensure that apparent national progress cannot conceal subnational vulnerability.