Malaria burden in Mozambique: Mozambique has the fourth highest burden of malaria worldwide, with an estimated 9 million cases in 2018 [1]. There were 10,132 deaths due to malaria in children under 5 years in Mozambique in 2017, with malaria as the top cause of post-neonatal deaths [2]. The prevalence of malaria has historically been higher in the northern provinces of the country, where there are more humid climates and higher populations (Figure 1).
There is substantial evidence linking long lasting in long-lasting insecticidal nets (LLINs) with reduced child mortality and morbidity. Universal coverage of LLINs is a core malaria prevention tool, and part of the first pillar of World Health Organization’s (WHO) Global Technical Strategy for Malaria 2016–2030 [3-5]. Globally, LLINs have become a core intervention of national control strategies with over 2.2 billion nets distributed worldwide as of the second quarter of 2020 [6].
Mozambique’s National Strategic Plan for Malaria (2017–2022) focuses on reducing the burden in high endemic areas while sustaining gains in low transmission areas to accelerate elimination. The plan emphasizes strengthening case management, universal access to diagnosis and treatment, strengthening malaria surveillance systems, and the continuation of universal coverage of LLINs as the main vector control strategy, with the use of indoor residual spraying (IRS) as a mitigation method. The National Malaria Control Program’s (NMCP) objectives relevant to LLIN distribution are to ensure that: 1) at least 90% of registered households have sufficient LLINs (at least one for every two people), and 2) at least 80% of LLIN owners sleep under their LLINs. The NMCP’s goal is to distribute one LLIN for every 1.8 people in the household every 3 years.
In Mozambique, the NMCP rolled out a national insecticide-treated nets (ITN) household ownership strategy in 2011, aiming to achieve universal coverage of LLINs throughout the country. Subsequently, through funding from the U.S. government’s President’s Malaria Initiative, and later from the Global Fund for Malaria Tuberculosis and AIDS, the NMCP worked with partners to organize mass distributions in all provinces. Between 2011 and 2019, 36,862,845 LLINs were distributed nationwide, starting in six provinces, culminating in the first countrywide campaign that delivered over 16 million LLINs to 95% of registered households in 2017 [7]. The 2020 campaign plans to deliver over 12 million LLINs to seven provinces but has been delayed by the COVID-19 pandemic.
Vital registration data to measure changes in mortality are not available in Mozambique and in most sub-Saharan Africa countries. Birth histories from national surveys are useful in measuring trends in all-cause child mortality, but they do not typically assess cause of death. There have been no provincial level mortality estimates in Mozambique since 2011. The Lives Saved Tool (LiST), developed by Johns Hopkins University, is a modeling application available through the Spectrum software package that estimates child mortality and “lives saved” for children under 5 years of age retrospectively and prospectively using the age structure of the population, fertility rates, under-5 mortality rates, cause of death structure, and changing coverage estimates of key child survival and maternal interventions [8]. The LiST child health intervention indicator related to LLINs is household ownership of an ITN and/or protected by Indoor Residual Spraying (IRS).
In Mozambique, previous LiST analyses have modeled the direct effect of the scale-up of malaria interventions (IRS, ITN household ownership, ITN use by pregnant women and IPTp during pregnancy) on reducing malaria-specific mortality from 2007 to 2011, and between 1997 and 2011 [9, 10]. These analyses linearly interpolated coverage between survey years to estimate ITN coverage while also increasing coverage of other maternal and child health interventions.
Junior et al. used historical coverage data and mathematical modeling to project future coverage levels for 22 interventions for 2015 to 2030, and then used LiST to estimate additional lives saved and changes in the child mortality rate over time [11]. However, the estimates did not take into account the actual number of LLINs distributed. Even so, the two interventions projected to save the most under-5 lives between 2015 and 2030 are increased coverage of artemisinin-based combination therapies (ACTs) and ITN ownership, contributing to an estimated 40.9% of the total lives saved if historical trends continue.
NetCALC is a tool that estimates how many bed nets are needed to reach a specified target for LLIN or ITN household coverage, or conversely, estimates ITN or LLIN coverage based on distribution of nets each year. The principal design of the NetCALC tool is a simple, compartmental model, and requires core population information, including: 1) the starting year, 2) the target population size during that year, 3) the average household size of the population, and 4) the average population growth rate [12-14]. The tool includes parameters on timing and size of actual net distributions, population and household size population growth, intra-household net accumulation, and net decay to project LLIN coverage at a given point in time based on the number of nets available for use for the specified target population. The tool has been used in previously published work [15-18].
In 2013, Paintain et al. used NetCALC and LiST together to estimate that the LLINs distributed between 2010 and 2012 in 40 countries in sub-Saharan Africa prevented about 350,000 malaria-attributable under-5 deaths compared to the baseline in 2009.
No previous analyses have estimated changes in mortality attributable to the distribution and scale-up of LLINs in Mozambique, accounting for heterogenous mortality rates, differences in disease patterns, and coverage of maternal and child health interventions between provinces. Most reporting and analysis on LLIN distribution has focused on outputs, such as the number of ITNs distributed by province or district. However, data on outcomes including mortality and lives saved can help stakeholders advocate for continued investment in LLINs as a cornerstone for driving and maintaining reductions in under-5 child mortality in Mozambique.
Further, the Mozambique NMCP usually calculates the number of LLINs needed annually, comparing the current method of calculating LLIN needs with provincial level evidence-based projections from NetCALC can help planners and policy makers to anticipate investments needed in LLINs, in order to more efficiently and effectively distribute them where most needed.