A retrospective review of vaccine wastage and associated risk factors in the Littoral region of Cameroon during 2016–2017

Immunization is strongly recommended by the global medical community as an effective preventive medicine to protect children and adults against infectious diseases [1, 2]. Although infectious diseases affect all countries, the burden is higher in many low-and middle-income countries (LMICs) where low vaccination coverage remains one of the major barriers against child morbidity and mortality associated with vaccine preventable diseases (VPDs) [3‐5]. Multiple factors may contribute to the uptake of vaccines and vaccination coverage including but not limited to the following: the availability of and access to vaccines; attitudes, perception, and health-seeking behavior towards vaccination by local populations; proper design and management of vaccination programs; appropriate administration of vaccines and vaccine types; vaccination target area characteristics such as urban and rural settings [2]; seasonality; and financial resources and capacity required for the execution and monitoring of immunization programs [6‐8]. Further, global vaccine prices may have budgetary and programmatic implications on new vaccine introductions in resource constraint countries, which may hinder vaccination coverage as an increased cost of vaccines adds a financial burden to the local medical care and health system [6, 9‐11]. While a comprehensive analysis of such factors affecting vaccination coverage is needed for different settings and countries, a review on vaccine wastage and its causes, challenges, and compromising effect on vaccination coverage could provide some insights on recommendations to reduce missed opportunities for vaccination [6].

According to the World Health Organization (WHO) report in 1997, nearly 43% of vaccines delivered to the developing countries were wasted, largely due to poor infrastructure [10, 12]. Aggregated national statistics showed disparities in vaccine wastage at the local level such as rural and urban settings [13], which were inextricably associated with challenges of infrastructure capacity. Other factors such as poor monitoring and tracking of vaccination programs [14], parents’ reluctance towards vaccination, concerns about vaccine safety, accessibility of health facilities especially in hard-to-reach communities, waiting time at health facilities, low educational level of the local population including both residents and health workers, population density, and logistical challenges in conducting vaccination programs also contributed to vaccine wastage in both rural and urban settings [15‐17].

In Cameroon, the Expanded Program on Immunization (EPI) began in 1976 as a coordinated pilot project of the Organization of Coordination for the Control of Endemic Diseases in Central Africa and became operational nationwide in 1982 [18]. The national EPI aims to prevent, control, and eradicate VPDs. Following the Declaration of the Reorientation of Primary Health Care in 1993, the EPI activities were integrated into the Minimum Package of Activities of health facilities nationwide, and the EPI vaccines were given to children free of charge, considering vaccination as a fundamental right of a child [18]. Although the immunization coverage of the EPI vaccines in Cameroon has gradually increased over the past decades, it still falls short of the national target, and there is sufficient evidence of missed or incomplete vaccination of eligible children [19]. Several reasons may explain this trend including the acceptance and uptake of national EPI programs by the general population, as well as challenges related to vaccine logistics and the management of vaccination programs [20] that aimed to not only increase the overall national vaccination coverage but also reduce vaccine wastage [21]. Vaccine wastage has a direct impact on immunization coverage as it translates to the availability of vaccines for use, especially in areas with poor access to vaccine storage facilities [6, 7]. Even when access to vaccine storage facilities is guaranteed, high vaccine wastage increases the cost of immunization programs because vaccine waste factors need to be considered when forecasting and planning the total number of vaccine doses required in each vaccination programs. In this context, reducing vaccine wastage to acceptable levels has been one of the measures recommended by the government of Cameroon to improve the national EPI vaccination coverage (Supplementary Table 1) [18].

The national EPI programs consider the population size of each targeted vaccine to estimate the total number of respective vaccine doses required as well as any potential vaccine wastage that may occur during the implementation phase of vaccinations. Routine monitoring of the vaccine wastage rate (VWR) of each EPI vaccine and utilization of field data for estimating needed vaccine doses are critical for appropriate management of vaccines for immunization programs; they also help avoid or reduce any missed opportunities of vaccination due to vaccine wastage. In this study, we aimed to investigate the VWR of EPI vaccines in the Littoral Region of Cameroon, including by analyzing risk factors such as type of vaccine, seasonality, and characteristics of vaccination sites, in comparison to the vaccination coverage rate (VCR) of respective vaccines. Our study findings may contribute to better understanding the factors causing vaccine wastage in Cameroon, proposing recommendations to improve the management of vaccines and planning, execution, and monitoring of immunization programs, and ultimately enhancing the national EPI coverage.

To achieve the full effect of immunization, high vaccination coverage and low vaccine wastage are important. High vaccine wastage makes vaccines less available for use, especially in remote areas where access to the central vaccine storage facility is challenging. To avoid compromising public health efforts towards increasing the vaccination coverage of EPI vaccines and minimizing vaccine wastage, an accurate demand-forecasting of these vaccines for target immunization populations and regular monitoring of vaccine wastage at all levels are important. The general guidelines on the VWR per vaccine [26] notes the wastage rates of 50% for BCG and 25% for the measles vaccine are considered acceptable for reconstituted vaccines; 10% for OPV; 15% for liquid vaccines in multi-dose vials of 10 or more doses; and 5% for liquid vaccines in single or two-dose vials such as PENTA and PCV. Considering this standard, the VWRs of each EPI vaccine in Cameroon during 2016 and 2017 were at an acceptable level; the VWR of BCG remained around 31–33%, and the VWRs of OPV and PENTA were below 5%. Country-specific vaccine procurement and management capacities are essential to achieve such VWR targets. In Cameroon, the targeted VWR [21] under the routine EPI during 2016 and 2017 was influenced by the government’s commitment to provide more resources to the EPI program, such as setting up a comprehensive multi-year plan (MINSANTE: Comprehensive multiyear plan 2007–2011 of the expanded program on immunization, unpublished) and supplementary immunization activities in health districts with poor performance indicators.

In the Littoral Region of Cameroon, lyophilized vaccines showed a higher VWR. This finding is similar to that of an existing study from The Gambia [10], which showed higher wastage rates in lyophilized vaccines than in other types of vaccines. In our study, VWRs were lower than the findings from a study in Bangladesh [27], where the wastage rate for BCG was nearly 84.9%, followed by MR at 69.7%, and PENTA at 44.4%. Notably, the liquid vaccine IPV also exhibited a high wastage rate (17.9%) in the Littoral Region, which may be due to its introduction into the Cameroon government’s EPI program in June 2015 [28]. Its high VWR may be attributable to the early stage of vaccine introduction as typically experienced in any new immunization program [29]. Our study supports the existing literature on lower wastage rates for vaccines that follow the multi-dose vial policy (MDVP), as seen in other studies from the Northwest Region of Cameroon and Bangladesh [27].

Using opened MDVP vials within 28 days, provided the storage conditions are favorable [30], is expected to reduce vaccine wastage [31]. However, lyophilized vaccines (BCG, MR, and YF) must be used within 6 h after reconstitution, or at the end of the vaccination session, whichever comes first, after which these vaccines must be discarded irrespective of the doses used in the vial [32]. Hence, vaccine wastage of these vaccines is only avoidable during large-scale vaccination sessions, which last less than six hours. Therefore, lyophilized vaccines tend to have a higher wastage rate than liquid vaccines (OPV, IPV, PENTA, PCV, and ROTA) in the real-world setting.

Understanding the relationship between vaccination coverage and vaccine wastage is a basic starting point to investigating causes and risk factors associated with vaccine wastage. Optimally, if a vaccination program is conducted based on a well-planned immunization plan, such as proper microplanning involving effective community engagement and following the standard operating procedures of appropriate vaccine management, vaccine wastage should remain low and vaccination coverage high. Our study showed an overall negative correlation between vaccination coverage and vaccine wastage and presented the multifaceted risk factors contributing to vaccine wastage. The lower vaccination coverage may not necessarily be solely due to the unavailability of vaccines or high vaccine wastage. Conversely, low vaccination coverage may also cause high vaccine wastage as vaccines in stocks can be damaged at health facilities, resulting in insufficient vaccines to immunize the target populations. This is highly possible as leftover vaccines taken to outreach sites may not return to the cold chain in their optimal conditions [33] and may be discarded. Notably, our study found that in the Littoral Region of Cameroon during October and November 2016, the wastage of all vaccines decreased when vaccination coverage also decreased. This may be due to the lower availability of vaccines or adoption of strategies that helped reduce vaccine wastage but compromised vaccination coverage [6]. The former is the likely explanation in the Littoral Region as BCG was not available even at the central vaccine storage facility in Yaoundé during the study period. The lack of a particular vaccine has a demotivating effect on healthcare workers in organizing vaccination sessions, as they will need to reorganize such sessions when the missing vaccines becomes available. Further, parents are demotivated to come for vaccination if they are aware of frequent vaccine shortages.

Rural areas are characterized by a smaller, sparsely distributed population, resulting in conditions that favor a high VWR [13, 16, 31]. This has been the case in the Littoral Region, where over the 2-year study period, rural districts had higher VWRs. Compared to urban health districts that mostly employ a fixed vaccination strategy (children are brought to health facilities for vaccination), in rural districts, an outreach vaccination strategy is typically applied to reach people living in remote areas with limited access to health facilities [13]. Usually, vaccine vials taken out for this strategy do not return to the vaccine storage facilities if vaccine vial monitors (VVM; small stickers that adhere to vaccine vials and change color as the vaccine is exposed to heat, letting health workers know whether the vaccine can be safely used for immunization) are not in place. Existing studies have reported high VWRs in rural areas due to vial breakage while opening, the burden of cost expenditure, and improper handling and storage, all of which were often related to the lack of skilled personnel in rural immunization activities [7, 9, 16, 33]. Furthermore, the possibility of accidents occurring in rural areas leading to unopened vial breakage is higher than in urban areas. Relatively less skilled personnel may also be involved in rural immunization activities [31]. Not fully understanding the importance of vaccination due to a low educational level, rural populations tend to have negligent behavior toward meeting vaccination appointments [17]. This often leads to waste of open vials, especially lyophilized vaccines. Notably, such differences in rural and urban vaccine wastage were not significant in a study conducted in The Gambia, likely due to enhanced vaccine management and high vaccination coverage [10]. In the Littoral Region of Cameroon, attempts are being made to reduce vaccine wastage in rural areas and nearby health facilities by planning immunization sessions more strategically that included increasing the size of vaccinated target populations.

The two major seasons in Cameroon, dry and rainy, have a distinctively different effect on immunization activities. The rainy season is typically associated with poor accessibility to healthcare facilities due to deteriorating road conditions and frequent power failures, especially in rural districts. This negatively impacts the vaccine supply chain and increases accidents that result in wastage of unopened vaccine vials during the outreach sessions of immunization programs [34]. Typically, during the rainy season, parents are more likely to miss vaccination appointments, which may result in increased vaccine wastage, especially for lyophilized vaccines. This is probably why vaccine wastages for BCG, MR, and YF vaccines were higher during the rainy season than dry season in 2016. Although the dry season is very dusty, it has favorable weather, road, and energy supply conditions. However, in the dry season, ambient temperatures are higher, which may lead to high vaccine wastage if compounded with inadequate cold chain facilities. This likely explains what happened in 2017, when the VWR for all vaccines was higher during the dry season in the Littoral Region.

Our study has also found that some vaccines, particularly PCV and ROTA, exhibited a negative VWR throughout 2016 and 2017. This may be related to poor data quality, which also limits confidence across other findings. However, it may be due to skillful health workers tapping the “extra dose” available in vials, which is due to vaccine manufacturers filling vials with excess volume [35]. Some VWR challenges related to certain vaccines are also closely linked to the respective vaccine cold chain requirement and management. Efforts are underway to develop vaccines that can tolerate extreme temperatures or being out-of-cold chain for a certain period or under monitored and controlled conditions [36]. The vaccines analyzed in this study are not available for controlled temperature chain (CTC) usage, but such CTC could be an innovative approach and contribute to reducing vaccine wastage and enhancing the vaccination coverage of at-risk populations living in rural, remote, or hard-to-reach areas with limited cold chain conditions and infrastructure. Our study also has limitations given that the analyzed data were available secondary data extracted from the government immunization records. The accuracy of the results presented depends on the accuracy of the source data accessed, and more in-depth analysis on the vaccine wastage rates for opened- and closed-vials could not be conducted.

Investigating vaccine wastage is important to better understand the reasons for VWR and plan for improved immunization programs going forward. To reduce vaccine wastage in the Littoral Region of Cameroon, emphasis should be placed on the risk factors related to rural areas during the rainy season (especially for lyophilized vaccines), and further investigation is needed to understand the causes of high vaccine wastage during the dry season. Improved vaccine cold chain systems should be put in place by investing in basic social infrastructure, such as adequate energy sources for field vaccine storage capabilities. Considering the diverse geographical and climatic characteristics of the Littoral Region, better vaccine demand forecasting with more real-time and site-specific monitoring of VWRs is recommended to prevent the inappropriate supply of vaccines. Further research is needed to more comprehensively analyze vaccine wastage across Cameroon, including by examining socio-behavioral aspects of vaccine acceptance and health-seeking behaviors of local populations to develop more refined public health immunization policy interventions in diverse settings.