Conceptual design and modelling approach

Spectrum-Malaria was designed for application in 43 sub-Saharan African countries with stable transmission of P. falciparum as the predominant species. Health effects of intervention scale-up in Spectrum are based on statistical functions fitted to simulations done in the OpenMalaria dynamic transmission model in the version Schema 32 [14] calibrated for P. falciparum [15]. Simulations and multivariate regression functions included as endemicity-related impact determinants: the annual entomological inoculation rate (EIR), the PfPR at 2000–2002, and the seasonality in malaria transmission. Simulated impacts for user-specified scale-up were statistically summarized for usage of insecticide-treated nets (ITNs), indoor residual spraying (IRS), seasonal malaria chemoprevention (SMC), and effective management of uncomplicated cases (CMU) and severe cases (CMS), as detailed in [16].

Spectrum applies these functions to first administrative level (Admin1) units (i.e., states or provinces) in a country [17], using Admin1-level endemicity, baseline burden rates and baseline coverage values available from the WHO and malaria atlas project (MAP) [2, 18, 19], in turn for a scenario of user-specified, intervention scale-up and a counterfactual of constant coverage. Proportional burden reductions associated with the user-specified scale-up are then aggregated across Admin1 units, and summarized as population-weighed, national proportional burden reductions, separately for two time horizons of interest (2016–2021 and 2022–2030). Next, burdens are projected over 2016–2030 for country populations defined in Spectrum’s module DemProj, by applying the relevant statistically predicted proportional burden reduction (separately for each age group, horizon and health outcome) to expected future counterfactual burdens for a scenario of constant coverage (Fig. 1).

Design of the Spectrum-Malaria impact module

The software package can be downloaded for free [20], with a user manual about installation and application available [21].