The systematized review indicates that of the 11 nations affected by the 2014-16 Ebola crisis (Spain, Italy, Liberia, Sierra Leone, Guinea, Mali, Nigeria, Democratic Republic of the Congo (DRC)Footnote 1 USA, Senegal, and the United Kingdom), nearly all maintained EVD-related policies for response and prevention, which in turn informed their COVID responses in 2020. In comparison, 164 (70.00%) of 234 non-EVD-affected nations had documented evidence of specifically adapting national systems to incorporate policy recommendations developed from the 2014-16 crisis. These nations tended to perform better in their response information management, outbreak containment in the first waves of COVID, more rapid and stringent policymaking, and higher rates of population compliance and mandate enforcement.

While most nations incorporated EVD-policies before 2020, they had no significant difference in 2020 cumulative COVID cases/million (t = -0.93, p > 0.05) or deaths/million (t = -0.76, p > 0.05), as COVID overwhelmed most national preparedness systems as the pandemic raged on. Our review found evidence of these changes in governmental documents, research, and health agency reports for 157 nations (64.01%). Comparatively, we uncovered media evidence for 108 countries (44.08%) reporting governmental public health reforms in direct response to the West African crisis. Secondary sources including media documenting these same changes triangulate and validate findings in official documents and research reports [42, 45, 46]. Yet it also indicates that while most nations made EVD-related changes before COVID, these reforms may not have been readily publicized, as reflected by the lack of media coverage. Whether past policies failed or were successful, policy legacies can help the policy learning process [20, 23, 35].

Table 2 summarizes the level of evidence of EVD-related policy activity, from no evidence to high among the three main groups of policy legacy & learning. The first group is comprised of countries that were not directly affected by the 2014-16 outbreak (no deaths or cases), and appear to have no evidence in the literature of any adoption of EVD-related reforms before 2020. The second group are non-EVD-affected nations with some level of documented policy changes, most of which indicates that most of these countries adopted EVD-related policies, and conducted moderate policy activities like agency trainings, WHO technical consultations, and some protocol reforms and governmental resource allocation. The third policy legacy group is nations with EVD cases and deaths, most of which additionally demonstrated moderate policy activity, while a handful have strong policy reforms at the national systemic level (triangulated by media sources).

The policy legacy of the 2014-16 EVD crisis may have been unique as a transcontinental biological threat that helped propel both international agencies and most national governments to take the threat of an imminent global outbreak more seriously [21, 47,48,49,50,51]. The systematic review indicates that many governments adopted and maintained public health policies developed out of the West African crisis, many of which were applied, modified, or repurposed for national COVID preparedness and response efforts. While institutions and decisionmakers may prefer maintaining the status quo, “there can be path departures in the absence of critical junctures since change can be exogenously spurred by cataclysmic events” [28].

Our analysis identifies four key variations in how countries incorporated EVD-related policies, which we categorize as: denial, reactive, strategic foresight, and retrospective learning. These categories help us discern between types of learning experiences and quality of responses, and map common country policy legacy trends against one another [52]. Figure 2 depicts the disaggregation of policy learning trends (called conditioned policy learning) and how the 245 WHO nations eventually fall into one of the four categories in relation to their 2020 COVID responses.

Conditioned policy learning of 2014-15 Ebola policies on WHO nations & COVID response

Most countries that experienced the 2014-16 crisis firsthand (Ebola cases and/or deaths) maintained their policies, infrastructure, and public health systems adapted during EVD when COVID struck, reflecting retrospective conditioning. Comparatively, our analysis notes that some countries (both EVD-affected and non-affected) appear to have lingered in the condition of denial. Additionally, some countries that did not directly experience the West African EVD crisis remained in a state of denial when COVID first struck, and at first demonstrated hardly any policy response action. They did not have stringent COVID policies in the first months of 2020, and did not have a national-level shutdown typically until after April 1, 2020 (weeks after the WHO declared a state of emergency).

Comparatively, other non-EVD affected nations that had no documented EVD-related policy changes before 2020 quickly took prompt action to COVID in March 2020, but often in a chaotic manner (reactive conditioning). Their stringency levels of COVID mandates fluctuated throughout the spring and into summer. However, most non-EVD-affected nations applied EVD-related policies from the West African crisis, often recommended by the WHO and CDC, in the years following the outbreak. When COVID struck, these countries purposefully applied the EVD-related policy modifications in their COVID response plans (a condition of strategic foresight). The next section elaborates on these variations in policy legacies and policy learning.

All nations that experienced at least one EVD case in 2014-16 had documented evidence of proactively adapting their health systems based on Ebola-related research, policy reform, and infrastructure and funding changes (measured by official government documents, agency documents, and/or media coverage). Yet, only ten of the 11 EVD-affected nations were able to retrospectively prepare and respond to COVID-19, meaning that they reactivated EVD-related policies when COVID first hit in 2020.

Reviewed governmental and health agency documents specify that these ten countries were frequently reapplying or modifying their Ebola-response mechanisms (including community engagement, case tracing, rapid testing, and quarantining procedures) to respond to COVID. This transition was frequently marked by quick reaction by the government, a stronger ability to mobilize preventative actions that signal containment of the disease, instead of inconsistent and cumbersome policy decisions with limited impact.

By the end of March 2020, stringency levels peaked worldwide with most nations locking-down before April. On March 31, 2020, the average stringency (low 1-100 high) in the 11 EVD-affected countries was quite high at 77.10 (SE = 3.41, CI95% 69.49-84.72). EVD-affected nations able to flatten the curve of the first COVID-19 pandemic wave tended to benefit from proactive planning on parts of national governments and international health stakeholders [50, 52,53,54]. As COVID struck in early 2020, these ten countries took decisive action to build on the health systems, infrastructure, and mechanisms put into place during Ebola.

Figure 3 provides case examples of EVD-related countries’ policy learning. Nigeria and Liberia’s COVID-19 national response in 2020 were notably organized and effective at mitigating the first waves often attributed to their EVD-related policy improvements [21, 22, 55,56,57,58]. One critical factor repeatedly noted is how many of these nations employed a key lesson learnt in the Ebola crisis- the need to identify culturally and contextually appropriate solutions [13, 21, 49, 51, 59]. Some initial Ebola policies promoted by international agencies, like body cremation, proved ineffectual, clashing with cultural beliefs and practices. Changes were eventually made to incorporate culturally-sensitive solutions proposed by West African experts [5, 11, 48, 59, 60]. Our health community was reminded of the importance in applying robust frameworks like the PEN-3 model, which are designed to guide global health experts and practitioners to carefully listen to cultural communities. We must first focus on the best practices of localized populations instead of starting with what global health policy dictates as wrong. “[S] ocietal reasoning and rationale are at the foundation of the message… reframing COVID-19 communication messages globally must respond not only to individuals but to the community as a collective” [47].

Case studies of EVD-affected countries & COVID-19 conditioned learning

A second key factor appears to be in national leadership determining to maintain EVD-related policies even after large shifts in political power such as after an election. We can view this in the 2020 decision by President Weah’s administration to actively support rapid implementation of national response protocols set during Ebola under his rival President Johnson-Sirleaf’s term in office [25, 57, 61]. The effectiveness of Liberia’s 2020 COVID response under Weah’s administration has been compared to the responses of China, New Zealand, and Finland [56, 57, 62, 63].

In contrast, Sierra Leone appears the only 2014-16 EVD-affected country to remain in a temporal state of denial during early 2020 as COVID spread. Evidence indicates delayed government response activity, less stringent policies (46.3/100 in late March), and a late lockdown. Several EVD-affected nations like Sierra Leone and Liberia reported low COVID infection rates in 2020. However, Sierra Leone’s low infection rate is widely debated within the health community. Despite its high EVD rates in 2014-16, COVID testing among Sierra Leone’s population remained effectively non-existent through 2022. Furthermore, a 2018 political shift led to the undoing of many EVD measures under the former administrative leadership [61, 64, 65].

Although they were not directly impacted by the West African crisis, the review found that 164 (70.00%) of the 234 non-EVD-affected nations had documented evidence of 2014-2019 policy modifications directly attributed to this specific epidemic. These modifications often were based on WHO-related recommendations developed from the West African crisis. Comparatively, 161 nations exhibit what we term strategic foresight (SF) conditioning by rapidly activating EVD-related system modifications by early March 2020 to combat COVID. Comparatively, three nations instead exhibit delayed denial responses (little COVID-response until April). The average end of March stringency level of SF nations was 75.35 (SE = 1.41, CI95% 72.61-78.16), with no significant difference compared to EVD-affected nations (t = -0.31, p = 0.62).

Our analysis indicates that often SF nations received guidance by lead international health organizations. The World Bank’s International Development Association-supported Regional Disease Surveillance Systems Enhancement (REDISSE) Program was launched in 2016 to support 2014-16 EVD-affected nations and non-affected nations (Benin, Burkina Faso, Cabo Verde, Cote d’Ivoire, The Gambia, Ghana, Guinea-Bissau, Mali, Mauritania, Niger, Nigeria, Senegal, Togo) to incorporate EVD-related policies to better guard against future epidemics. To varying levels of degree, these countries included REDISSE health reforms to combat COVID, including rapid laboratory testing, forming a technical preparedness working group, and activating Incident Action Plans transnationally [22, 66,67,68].

Additionally, after the West African Ebola crisis, nations performed self-assessments of their preparedness systems using a WHO checklist as part of the International Health Regulations Core Capacity Monitoring Framework. Moreover, technical missions were performed in 27 Latin American and Caribbean nations like the Bahamas to identify potential EVD cases within their territory. This required working in partnership with global health policy experts from national agencies and key national agencies [69]. Most of these countries activated elements of the IHR training in 2020. Yet even with this training, some nations like the British Virgin Islands remained in a brief state of denial, with no documented evidence that the nation learned from Ebola, and furthermore, greatly delayed in responding to COVID-19, with concerns of economic fallouts [70, 71].

Comparatively, our review did not reveal any documented evidence for 70 nations of incorporating EVD-related changes prior to 2020, of which 19 remained in a state of denial when COVID struck. Comparatively, 51 demonstrated reactive conditioning. For instance, the Bulgarian Parliament unanimously passed a declaration a state of emergency, with a 14-day preventive house quarantine for citizens traced to contact with a COVID-19 patient or a highly-infectious nation [72]. Reactive conditioning was often chaotic, but at times, some nations were able to react efficiently and effectively, provided they had proper resourcing and expertise. Overall, these 70 nations had a modestly lower average stringency rate around the end of March 2020 of 72.75 (SE = 3.61, CI95% 65.43-80.06), just as COVID began to first peak worldwide. Research indicates that the impact of the timing and level of mitigation policies in the spring of 2020 were generally important for lowering mortality from COVID-19 [61, 73, 74].