LLINs are the mainstay of malaria control in Uganda. To ensure Ugandans have access to LLINs, the Ministry of Health delivers free nets through mass distribution campaigns every 3–4 years. However, achieving and sustaining high LLIN coverage remains a challenge. To better understand the impact of Uganda’s campaign to distribute LLINs in 2020-21, and factors associated with LLIN coverage and use, a cross-sectional survey was conducted 1–5 months post-distribution in 12 districts across Uganda. Considering several key LLIN indicators, the 2020-21 campaign was a success. Over 93% of households owned at least one LLIN distributed through the 2020-21 UCC, and over 70% of residents reported sleeping under a UCC LLIN the previous night. However, less than 60% of households owned at least one UCC LLIN for every two residents, which varied substantially by site, suggesting that the number of nets distributed to many households was insufficient to ensure adequate coverage. Prior studies in Uganda have highlighted that net attrition is also a major problem [2,12], with the lifespan of many LLINs less than the anticipated 3 years. Strategies to ensure that households receive enough nets to guarantee high coverage and access to LLINs must be employed in future mass distribution campaigns.
The WHO recommends distributing LLINs every 3 years through mass campaigns supplemented by delivery of LLINs through routine channels, such as antenatal clinics [7]. Uganda’s Ministry of Health and partners have maintained commitment to mass distribution campaigns, and the success of the 2020-21 campaign, despite the ongoing COVID-19 pandemic, is remarkable. Contributors to this success include the door-to-door distribution model, which allowed the team to access individual households. Lockdowns and movement restrictions imposed to mitigate the spread of SARS-CoV-2 in Uganda may have also confined adults at home, making it easier to locate them and to distribute LLINs to individual households. Use of an electronic database to register households and residents, and to allocate the number of LLINs at the household level, was another major advance; in prior UCCs registration data were entered by hand and aggregated to determine the number of LLINs to allocate at the level of the subcounty [17]. This aggregated approach was susceptible to errors of omission, leaving some households without LLINs. Future campaigns should leverage and build on the electronic database established for this campaign to more accurately estimate the number of LLINs needed in advance to guide procurement, and to calculate the number of LLINs required in each household.
In this study, the strongest predictor of adequate coverage with UCC LLINs was the number of household residents; the odds of adequate coverage with UCC LLINs were 13 times higher in households with only 1–4 residents than in those with 7–14 residents. Wealthier households, and those led by older individuals and female heads of household, were also more likely to be adequately covered by UCC LLINs. In the 2020-21 campaign, the number of LLINs distributed to each household was restricted to a maximum of five nets, regardless of household size. The practice of capping the number of LLINs distributed was likely the major contributing factor to inadequate LLIN coverage [7]. In future LLIN campaigns, strategies to increase the number of nets available for distribution (starting with adequate procurement), and to ensure that large households receive the correct number of LLINs to cover all residents (avoiding any blanket approaches to restricting the number of LLINs distributed) should be adopted. Routine distribution channels should also be strengthened to fill any gaps resulting from insufficient delivery of nets in the mass campaigns, which will be compounded by net attrition over time. In Uganda, LLINs are routinely distributed to vulnerable groups through the Expanded Program on Immunization, antenatal clinics, schools, and community health workers. Approaches to expand these routine channels, and to target poorer households and households led by younger males, should be explored.
Achieving adequate LLIN coverage is an important step toward maximizing access and use of LLINs. In this study, 86% of residents of households that were adequately covered with UCC LLINs slept under a LLIN the previous night, compared to only 62% in households that were inadequately covered. This link between adequate LLIN coverage and use of LLINs has been demonstrated elsewhere [18–21]. In western Kenya, households with more residents were less likely to own adequate numbers of LLINs, which strongly reduced the likelihood of using LLINs [18]. Similarly, elsewhere in Africa, including the Democratic Republic of Congo, Zambia, and Madagascar, as well as in Papua New Guinea and India, LLIN use was significantly higher in households that were adequately covered, with low LLIN coverage the main barrier to LLIN use [19–23]. In Tanzania, two years following a mass campaign, larger households, including those with more than four residents, were less likely to have access to, and to use, LLINs [24]. In Ethiopia and southern Africa, a study of over 6,000 households found that household size was associated with lack of equality in LLIN ownership and use of LLINs [25,26]. These findings suggest that improving LLIN coverage would likely increase use of LLINs.
School-aged children were less likely to use LLINs in this study than younger children or older residents, regardless of whether they lived in a household that was adequately covered with UCC LLINs, or not. LLIN use among children aged 5–15 years from inadequately covered households was particularly low (< 60%). Multiple studies have found that school-aged children are less well-covered by LLINs [10,12,27]. These older children are often overlooked by malaria control strategies, which have traditionally focused on children under-five and pregnant women who typically bear the burden of malaria morbidity and mortality in higher transmission areas [28,29]. Older children, who have developed anti-disease immunity through repeated exposure, are often asymptomatic when infected with malaria parasites. As a result, malaria infections in this age group may be missed. Malaria in school-aged children is not benign, however; older children may suffer consequences of malaria including clinical malaria episodes, anaemia, and cognitive impairment [27,30]. School-aged children typically have the highest prevalence of asymptomatic malaria infection in higher transmission areas, serving as important reservoirs of infection for onward transmission of malaria [31–33]. Moreover, as the epidemiology of malaria in Africa evolves in response to intensified control efforts, increasing urbanisation, and climate change, transmission intensity and exposure to malaria parasites will decline, and consequently, acquisition of immunity may be slower. As a result, older children could have less robust immunity to malaria, and be at higher risk of clinical consequences of malaria infection. Studies conducted in Uganda, and Mali report shifts in the burden of malaria to older children [34–36], supporting this theory. Strategies such as school-based interventions aiming to improve LLIN coverage and use in older children are gaining traction. In Tanzania, a study to evaluate a school-based LLIN distribution programme found that LLIN use increased from 57–77% among primary school children [37]. Targeting school-aged children, who can serve as agents of change, can also improve LLIN use within households [38].
In this study, relationship of household residents to the head of household was associated with LLIN use in all households, regardless of LLIN coverage, suggesting that hierarchy and status within households may influence LLIN access and use. The odds of using a LLIN were 3–4 times greater for heads of household compared to second-degree relatives or unrelated residents. In households that were inadequately covered by UCC LLINs, less than 60% of distantly related household residents used an LLIN. This finding is somewhat unexpected given that settlements in most African countries tend to function as close units, irrespective of whether household members are nuclear or extended family [39]. However, a prior survey in Uganda also identified relationship to the head of household as a factor strongly associated with LLIN use, with second-degree relatives and unrelated household members less likely to use LLINs that household heads, regardless of adequate LLIN coverage [12]. Similarly, in Kenya, non-nuclear family members were less likely to use nets than residents closely related to the head of household (nuclear vs nonnuclear members, aOR = 4.75 (2.89–7.81) and aOR = 4.16 (1.40–12.38) in highland areas and lowlands respectively) [18]. In this study 15% of household residents were second-degree relatives or not related to the head of household. However, we were not able to explore these relationships, or to gain an understanding of whether these residents are permanent, or more transient, members of the household. An in-depth understanding of this population, including their role in the household and household dynamics is needed, to ensure that this vulnerable group is better targeted in future LLINs campaigns and interventions.
This study had several limitations. First, an in-depth understanding of why household residents use LLIN, or not, is limited by the quantitative nature of the questionnaire used in this survey. Further exploration of these important issues using qualitative research methods is needed to better understand determinants of LLIN use within households. Second, target areas included only a few villages surrounding the MRCs, which may have limited generalizability of these findings. However, all statistical models adjusted for site-specific clustering, to minimize any bias arising from the non-representativeness of few villages, and included conservative standard errors [40]. Third, LLIN use was self-reported, which could have under- or over-estimated actual LLIN use, but is the standard approach to measuring LLIN use [41].