Nigeria has been one of the largest recipients of health aid since 1999, and most critical public health interventions in the country are largely funded by donors (Organisation for Economic Co-Operation and Development [OECD] 2019). Nigeria received over 10 billion dollars in official development assistance (ODA) in just 2 years between 2013 and 2015; 49% of this assistance was allocated to the health sector (OECD 2016a). In 2017, Nigeria was the top recipient of ODA to the health sector (OECD 2019). Despite the collaborative efforts of Nigerian government, donor agencies and nongovernment organisations (NGOs) to implement efficient and effective health interventions, problems of sustainability leave these efforts much to be desired with donor-supported programmes fraught with limited effectiveness, scarce impact and low sustainability (European Commission 2010; Smith 2012). For many years, the question of what happens to health intervention beneficiaries when donor funding for implementation expires and ways to measure this has persisted (Bossert 1990; Cekan 2016; Mancini & Marek 2004; Proctor et al. 2015). This question is especially pertinent for Nigeria where despite billions of dollars received for funding of health programmes over the past years, very little is known about their sustainability (European Commission 2010). With the decline in donor funding, the question of how to effectively allocate limited resources with a more pronounced aim of sustainability is germane. As a result, sustainability has become an important global target to achieve.

There have been various definitions of sustainability proposed over the years (Gruen et al. 2008; Jha et al. 2016). The OECD’s Development Assistant Committee criteria for evaluating development assistance defined sustainability as ‘concerned with measuring whether the benefits of an activity are likely to continue after donor funding has been withdrawn’ and emphasised the importance of financial and environmental sustainability (OECD 2016b). Scheirer and Dearing (2011:2061) defined sustainability as the ‘continued use of program components and activities for the continued achievement of desirable program and population outcomes’. Rogers and Williams (2008) proposed that sustainability does not always involve continuity of projects and can sometimes be sustained capacities of individuals and organisations, funding, participation and ideas.

Much of the focus on sustainability of development projects in Nigeria has been on the continuation of funding for projects, rather than assessing post-project impact (Adekeye 2014; Mirzoev et al. 2015). While some organisations have done a few investigations or assessments to evaluate the sustainability of various development projects in Nigeria (Japan International Cooperation Agency 2012; KfW Development Bank 2014; The World Bank 2014), only a few talked to stakeholders in a methodologically detailed way to include participant voices in such evaluations. Returning to the field years after the end of the project to ask project participants and partners what benefits were sustained, why some outcomes were sustained and others were not, and make recommendations for future projects is key to Sustained and Emerging Impacts Evaluation (SEIE) (Cekan 2016; Iwelunmor et al. 2016). It avails the opportunity to evaluate the endurance of improvements shown at the end of the project such as changes in knowledge, attitude, behaviour, beneficiaries’ health and education status, impact on infrastructure development, and individual and community empowerment.

Different attempts have been made to identify potential influences on sustainability. Stirman et al. (2012) in their review of sustainability of new programmes and innovations identified studies from a variety of fields, but the applicability of their findings to any one sector including the health sector may be somewhat limited. Also, only one Nigerian study was included. In another review, Iwelunmor et al. (2016) proposed the dynamic sustainability framework which emphasised some major elements for sustainability such as the intervention, the context in which the intervention is delivered and the broader ecological system within which health and healthcare systems exist and operate. The review examined studies across different settings; however, it may be difficult to generalise its findings to the Nigerian context.

While sustainability is a desired outcome of effective implementation, there has been little research-based evidence in this area in Nigeria (Iwelunmor et al. 2016; Smith 2012). This article aims to explore the overall body of knowledge on the evaluation of sustainability of health programmes in Nigeria, and to analyse factors identified as potential facilitators or barriers to the sustainability.

Post-project evaluation remains an important, but still rare, event in the project cycle. While most international development projects aim and claim sustainability of their interventions, fewer than 1% of development projects are evaluated after funding ends (Cekan & Zivetz 2016; Zivetz et al. 2017). Funding for evaluation usually ends when projects close and there may be little political interest to focus on sustainability as opposed to seeking funding for new programmes.

Organisations may also feel pressured to fit their activities within the funder’s priorities leading to donor influence on priority setting and fixed timeframes for implementation, funding and reporting as well as feedback on what could be sustained, how and by whom (Lee & Lim 2014). This reduces the chances of sustainability when donor funding stops.

Domestic financing for health intervention in Nigeria has grown over the years, but still falls below par because budgetary allocation to the health sector is below the 15% minimum contained in the Abuja Declaration (Uzochukwu et al. 2015). This affects the capacity of the government to sustain health interventions when donors leave.

Often, donor funds are used by health programmes to pay for community involvement and participation (Amazigo et al. 2007). This can create an expectation of external support and enthusiasm for cash which may lead to unsustainable development.

Decisions about how long to evaluate sustainability after project close remain highly contextual and no specific deadline exists. However, some authors have suggested waiting at least 2 years from close of project to ensure residual inputs from the project have ceased (Cekan 2015; Zivetz et al. 2017). None of the studies referenced post-project achievement in terms of original project targets. This raises questions about how organisations select and report on what they evaluate to determine sustainability.

All of the studies reviewed referenced the importance of community ownership and involvement for sustainability. Numerous studies have also corroborated the effectiveness of community participation in the sustainability of health programmes (Anderson, Brown & Jean 2012; Preston, Waugh & Taylor 2009; Rosato et al. 2008). Participants’ perspectives about their organisational and initiative-specific sustainability needs and wants onward are pertinent. Sometimes participants are unaware of responsibilities of their own or of their community. In these cases, sensitisation and education could overcome initial apathy and generate community support (Goldberg & Bryant 2012; Preston et al. 2009). Even then, community strengths may not overcome some of the weaknesses further up in the health system.

The importance of building the capacity of programme partners has also been emphasised as part of strengthening health systems and ensuring sustainability (Bennett et al. 2011; Goldberg & Bryant 2012; Sharma et al. 2013). Bennett et al. (2011) reported on how building the capacity of implementing partners such as government staff members, NGO and community through training and mentoring to build their technical and managerial skills helped in the transition of the Avahan HIV Prevention Program in India to local ownership (Bennett et al. 2015). An ex-post report for the Joint Regional HIV/AIDS Project suggested that conditions for sustainability would have been more favourable if there was focus on capacity development in the implementation of activities and the creation of durable mechanisms for cooperation and system performance (GIZ 2012).

Two of the studies reviewed emphasised the importance of leadership, effective linkages, collaboration and partnership for sustainability (Amazigo et al. 2007; Burlew et al. 2014). Other studies have also shown it is necessary to identify opportunities for collaboration between partners to use resources more efficiently, reduce duplication of effort and ensure sustainability (Iwelunmor et al. 2016; Osawa, Kodama & Kundishora 2010).

A TOS developed at the design phase has the benefit of being able to track sustainability. Organisations should have a plan for transitioning to sustainability after projects close (Cekan & Zivetz 2016; Zivetz et al. 2017). This should include handover plans to local nonprofits, with training and financial support; training for communities on how to manage the sustainable activities it prioritises and financing mechanisms for those activities. Some authors have suggested the inclusion of a natural comparison group during post-project evaluation to effectively compare sustained impact (Zivetz et al. 2017). Post-project evaluations should provide more detailed methodologies and put more focus on direct beneficiary participation in the evaluation process.

A clear understanding of operational indicators for sustainability, embedding sustainability early in the project cycle, country ownership, community involvement, capacity building, effective collaboration and quality post evaluation are key for sustainable development in Nigeria.

Evaluating sustainability of health interventions has the potential to demonstrate the extent to which practices are replicated through anticipated and unanticipated pathways (Zivetz et al. 2017). By identifying unexpected and emerging outcomes that came about post-project – outcomes that were not anticipated in the design – we improve upon our understanding of best practices for sustainability, and ultimately the quality and relevance of the subsequent interventions.

A limitation of this review is the small number of studies included. However, we chose to exclude evaluations done less than 2 years post-implementation and reports without qualitative or quantitative research methods. Secondly, because of heterogeneity in definition or description of sustainability in the studies and assessment of sustainability at a single point in time, we could not compare outcomes and changes over time.

This review explored the overall body of knowledge on the evaluation of sustainability of health programmes in Nigeria as well as potential facilitators or barriers to the sustainability. We also investigated definitions and methodologies adopted in a range of post-project evaluations for sustainability and how approaches used in evaluation have enhanced or challenged post-project assessment.

There is a dearth of research on evaluation of sustainability which can be seen from the small number of such evaluations relative to hundreds of thousands of health projects implemented in Nigeria. Such evaluations may be seen as too hard, too expensive, not important or just plain unnecessary. Sometimes, when they are done, they may be seen as incriminating, and thus not shared. Further research is required to provide rigorous evidence base to explore evaluation of sustainability in Nigeria. Research should also seek to understand the views of key stakeholders such as donors, implementing partners and government on evaluating for sustainability. This will contribute immensely to the development and implementation of sustainable interventions.