The International Health Regulations (IHR) are a set of legally binding global health rules adopted by World Health Organization (WHO) Member States to prevent, detect, and respond to events with the potential to cross borders (1, 2). They define the rights and responsibilities of Member States and provide a vital legal framework for global health security, obliging countries to enhance their capabilities in disease detection, assessment, and reporting (1, 3, 4). Through their implementation, the IHR empower the WHO to coordinate international responses to public health emergencies, ensuring timely information sharing and collaborative action among nations (5, 6). This includes the recent IHR amendments, which provide WHO Member States with renewed motivation to adopt domestic legal and policy frameworks to facilitate IHR implementation (7, 8). Given the interconnectedness of health systems, collaborative mechanisms, and IHR core capacities, a One Health, all-hazards, whole-of-government approach is considered a critical component of IHR implementation for safeguarding global health security (9, 10).

While the IHR aim to ensure effective and efficient coordination in the prevention of, and response to, public health emergencies of potential international concern, they are inherently associated with numerous challenges and criticisms, including limitations, ambiguities in the text, and difficulties in coordinating multisectoral responses during crises such as epidemics and pandemics. Reforms have therefore been undertaken to address these shortcomings (8, 11–13).

For the successful implementation of the IHR, the WHO established components and indicators for each capacity and capability in State Parties to support monitoring, evaluation, and identification of implementation gaps. Countries are required to report progress on achieving the core capacities through an annual multisectoral self-assessment process known as the State Parties Self-Assessment Annual Reporting (SPAR) (14), as well as through voluntary, external, peer-reviewed Joint External Evaluations (JEE) (15). The JEE and SPAR tools allow countries to report on their core capacities to prevent, detect, and respond to public health threats, providing critical interim data on IHR compliance and identifying deficiencies to guide strategic planning through the National Action Plan for Health Security (NAPHS) (4, 16).

The NAPHS serves as a blueprint for countries to systematically strengthen their health security frameworks and respond to emerging health threats. The monitoring and evaluation of its delivery are vital for assessing progress on IHR core capacities, identifying constraints such as funding and coordination challenges, and guiding governments toward effective, prioritized health initiatives with measurable outcomes. There is reported progress has been made globally in the implementation of NAPHS to enhance health emergency capabilities (17). Despite this, there have been documented challenges from various countries in the development and implementation of NAPHS, particularly with respect to the quality of monitoring, evaluation, and data systems (18).

Sierra Leone’s first NAPHS (2018-2022) was developed based on findings from the first JEE conducted in 2016, involving the 19 technical areas of IHR. The development, implementation, and monitoring of NAPH is particularly relevant to Sierra Leone, because of the country’s fragility to public health threats, and its health system has been shaped by recurrent shocks from the 2014–2016 Ebola epidemic to the COVID-19 pandemic, alongside other natural disasters like floods and landslides that periodically disrupt services and supply chains (19, 20). This inaugural NAPHS had its implementation period extended to 2024 to accommodate COVID-19 and resourcing delays. The implementation from 2018 to 2021 led to improved Joint External Evaluation (JEE) scores, reflecting enhanced capacities in both human and animal health sectors, despite challenges such as COVID-19 disruptions and inadequate health infrastructure, as documented in our previous work reported by Njuguna et al. (21). However, the review was based on the NAPHS operation plan and the performance scores of JEE, which missed critical and more recent changes in the JEE and SPAR scores between 2021 and 2024.

Although many countries have developed and published their NAPHS, including those in the Global South such as Tanzania (22), Cameroon (23), Pakistan (24), Nigeria (25), and Uganda (26), there is limited published evidence on programmatic reviews of NAPHS implementation using robust mid- and end-term (MET) evaluations. This study therefore uniquely assesses progress in NAPHS implementation through MET evaluation processes and interrogates these findings alongside JEE and SPAR performance scores. This study is important because it consolidates critical monitoring and evaluation time points for planning and reporting progress in NAPHS implementation across 19 technical areas, and the resulting findings and lessons will be relevant to national and global health security stakeholders.

To our knowledge, this is the first study to evaluate the implementation of a NAPHS at both mid-term and end-term, alongside two IHR capability assessment processes. Over the 7-year period (2018–2024), Sierra Leone’s first NAPHS experienced both notable successes and persistent challenges in its implementation.

We identified five key lessons from this review that are relevant to policy and practice in global health security, particularly in comparable contextual settings such as Sierra Leone. First, implementation progressed at a faster pace during the first half of the NAPHS period but slowed considerably during the second half, up to 2024. The overall implementation rate increased substantially at mid-term, reaching 56% in 2021. This represented a notable achievement, indicating that the plan’s goals and objectives were being met more rapidly in the initial phase of implementation. However, by the end of the term in 2024, implementation had slowed more than initially anticipated, reaching only 65%. This slowdown can be partly explained by the destabilization of health security architectures during complex emergencies and crises, such as the COVID-19 pandemic and concurrent humanitarian emergencies (11, 27).

Second, although there was an overall increase in implementation rates, a substantial proportion of activities remained incomplete. By the end of the NAPHS term, only 39% of planned activities had been completed, leaving a significant gap in the delivery of intended health security outcomes. A particularly concerning finding was that 13.3% of planned activities had not been initiated at all, while the majority (63%) remained in progress. These findings are consistent with observations from Uganda, where 65% of NAPHS activities were still in progress, albeit from a smaller set of 96 activities compared with Sierra Leone’s 166 activities (26). This level of inaction raises questions about the realism of completing the plan within the specified timeframe, while also pointing to gaps in governance and financing structures, as well as limitations in the capacity of implementing entities to prioritize and execute planned activities.

Third, the findings revealed a more complex and nuanced pattern of performance across technical areas (TAs). There was a consistent increase in activity completion rates across all TAs except Food Safety, reflecting steady progress and underscoring the commitment of several implementing agencies. Six TAs emerged as high performers, achieving completion rates of 87% or higher at end-term, while eight TAs, with completion rates ranging from 42% to 83%, demonstrated substantial progress in implementing planned activities. In contrast, five TAs lagged behind, with completion rates of 42% or lower. Although progress was evident across most TAs, the observed variation highlights areas requiring additional support and targeted resource allocation to ensure overall plan success.

Fourth, the NAPHS demonstrated gradual progress in strengthening IHR core capacities. Only modest improvements were observed in SPAR scores, which increased from 51% in 2021 to 55% in 2024. More pronounced gains were seen in specific TAs, including Legislation, Human Resources, Food Safety, and Chemical Events, where scores improved by up to 20% between 2021 and 2024. While these TAs recorded substantial score improvements, it is notable that Food Safety, Chemical Events, and Radiation Events remain among the lowest-scoring IHR core capacities in low-income and lower-middle-income countries (28). The sustained high performance of Surveillance, maintaining a score of 80%, is assurance for sustaining active public health intelligence and outbreak detection capacities, using innovative tools and technologies for integrated disease surveillance since the 2014 Ebola outbreak (29–32). In contrast, two previously high-performing TAs—Health Emergency Management and Risk Communication—experienced notable declines in scores, raising important concerns that warrant further investigation.

Fifth, the Joint External Evaluation (JEE) scores revealed a swing and roundabout pattern, with overall scores consistently lower than those of the SPAR assessment across all technical areas (TAs). The overall JEE score of 46% is substantially lower than the regional average reported by Talisuna et al. (33). However, some TAs, including Financing, IPC, Points of Entry (PoE), and Radiation Events, showed convergence with SPAR scores, indicating areas of relative strength and alignment. In contrast, other TAs, such as RCCE, Surveillance, and IHR Coordination, demonstrated comparatively higher scores, similar to NAPHS implementation performance. Conversely, consistently low scores were observed for Radiation Events, Chemical Events, Biosafety and Biosecurity, AMR, and Linking Public Health (LPH), underscoring persistent capacity gaps previously reported in multi-country studies (34, 35). The relatively lower JEE score in 2023 may be partly attributed to the use of the third version of the JEE tool, which introduced structural changes, including revised and additional indicators, such as the separation of AMR and IPC. This distinction is important, as previous studies have shown that some JEE indicators do not clearly align with SPAR indicators, and that certain TAs assessed in the JEE—such as AMR, Immunization, Biosafety, and Linking Public Health—are not explicitly captured in SPA (16). There was more progress on the IHR pillar for response, followed by prevention and detection, which is the case of many low- and middle-income countries with inadequate preparedness capacity to absorb the shocks of health emergencies (36). The JEE further highlighted progress in indicator-level capacity development, with 11% of indicators achieving level 4 (demonstrated capacity). However, similar to findings from other countries, Sierra Leone has not yet achieved demonstrated capacity across most, indicators, with 89% remaining below level 4 (34). We observed a structural disparity between NAPH’s priorities and financial obligations. Although most activities received funding, the largest portion of the overall budget still lies in activities that are either unfunded or not reported. This implies that present funding methods support smaller, less expensive interventions, which might yield gradual progress, while more expensive, saving those costly system-wide investments remain vulnerable to from the risk of postponement. To address this imbalance will require leveraging, it is necessary to leverage co-financing opportunities and prioritizing investments to maintain progress on cost-effective actions while crafting focused plans for high-cost interventions.

As the first NAPHS cycle concludes with several activities still pending, we recognize that budgetary constraints, political gridlock, the COVID-19 pandemic, and disparities among One Health actors continue to hinder full implementation. Moving forward, continuous monitoring and evaluation will be essential to refine strategies and sustain program effectiveness. Long-term implementation will depend on securing through domestic budgets and leveraging co-financing opportunities. Also building local capacity and institutionalizing emergency preparedness and response procedures within the routine healthcare systems—investments that are likely to yield dividends during will eventually pay-off in future outbreaks. Addressing these implementation challenges will require the National Public Health Agency and its partners to design and implement a more realistic NAPHS 2.0, grounded in sustained investment, bipartisan collaboration, and data-driven policymaking. Engagement at local, national, regional, and global levels has been shown to strengthen national resilience to future health emergencies (37).

The comprehensive, unique and participatory evaluation approach employed in this study, using WHO-recommended tools at two critical time points enhances its the credibility and policy relevance. of this study. However, limitations include the absence of a standardized NAPHS evaluation tool, reliance on consensus-based activity ratings of activities, and the inconsistencies between some of the JEE and SPAR indicators, which may constrain limit full impact assessment and generalizability. Despite these limitations, the study provides valuable insights to inform strengthening health security planning and guide future NAPHS iterations, particularly in similar resource-limited settings.

Our study documented key lessons, implementation realities, and pathways forward in delivering a complex plan such as the NAPHS within the context of IHR core capacities. Progress was slower than desired, particularly in the second half of the implementation cycle, with several activities remaining uncompleted and variable performance observed across technical areas (TAs). We did not observe consistent measures of NAPHS achievement when compared with JEE and SPAR scores across TAs, and a clear, but observable disparity emerged between NAPH’s priorities and associated financial obligations. With this slow progress, there is a risk in building core capacities for IHR implementation, especially where more improvement focuses on the IHR pillar for response.

Changes in IHR monitoring tools and indicators are likely contributing factors to the observed slow progress. However, persistent challenges—including domestic budget constraints, limited political backing, the COVID-19 pandemic, and disparities among One Health entities—have further constrained the plan’s full potential. Nonetheless, adopting a more holistic and adaptive approach could ensure that NAPHS 2.0 is sufficiently realistic and responsive to the diverse needs of implementing entities across TAs. Importantly, slightly shifting the narrative from a response-dominated focus toward stronger emphasis on prevention and detection will contribute to the continued strengthening of national preparedness and protecting public health against future emergencies.