Population-weighted distribution of expected ITN retention times and duration of use by country.
Median estimates of the mean ITN retention time and duration of use for each subnational region were weighted by population to produce country-level distributions. These histograms represent probability distributions of retention time and duration of use for an individual randomly selected from each country, assuming model-derived median estimates for all subnational regions. Subnational variability in retention times and the duration of use reflects differences in model-derived estimates between regions, since the model assumes these values are constant within regions. Vertical dashed lines indicate the overall population-weighted mean (black) and the population-weighted mean for each country (coloured). stop owning them, so that use given access is not constant but typically wanes as ITNs age (figure 2.A).
ITN use, access and Pf PR over time in rural Burkina Faso.
A: Survey estimates of ITN use (probability someone slept under an ITN the previous night, points sized proportionally to sample size) and model mean estimates of the probability of use over time (solid lines) for rural portions of subnational regions in Burkina Faso. Mean estimates are shown for the probability of access (dotted lines) and the probability of using an ITN sourced from a continuous channel (dashed lines).The model accounts for differing probabilities of use between individuals within a region; this results in notable uncertainty around the probability an individual selected at random uses a ITN. This uncertainty is illustrated in the shaded region, with the 50%, 80% and 95% credible intervals as indicated by progressively lighter shaded regions. B: Pf PR2−10 estimates from the transmission dynamics model (darker lines) were fitted to annual estimates of Pf PR2−10 from the Malaria Atlas Project (2024) (hollow points); model estimates of Pf PR6−59mo are also shown (lighter lines), in addition to observed DHS Pf PR6−59mo and associated 95% credible intervals due to measurement uncertainty (solid points and vertical lines). Figure 2—figure supplement 1. Use, access and Pf PR over time in rural Senegal. Figure 2—figure supplement 2. Use of ITNs from continuous channels.
Mean use and access with three-year campaigns in subnational rural areas.
Central estimates of mean overall proportion of people using an ITN the previous night, access to an ITN, and use given access for three-year mass campaign intervals are shown in the top three rows. The number of months following a mass campaign where overall ITN use exceeds 80% are shown in the bottom row. Figure 3—figure supplement 1. Mean use and access with three-year campaigns in subnational urban areas. Figure 3—figure supplement 2. Mean rural use and access with two-year campaigns. Figure 3—figure supplement 3. Mean urban use and access with two-year campaigns.
Equity of use and access in rural Thiès and Ziguinchor, Senegal.
Solid vertical lines denote overall ITN use and access averaged over three years following the last mass campaign. Coloured bars indicate the proportion of the population with different probabilities of using or having access to an ITN. For example, 10% of the population have a probability of access between 70% and 80% in rural Ziguinchor, in comparison to 20% in rural Thiès. Vertical dashed lines denote 50% credible intervals for the probability of an individual uses or has access to an ITN, indicating that half of the population are expected to have a probability of use or access within this range. Figure 4—figure supplement 1. Subnational equity of use in Senegal. Figure 4—figure supplement 2. Subnational equity of access in Senegal.
Retention time, use given access and changes in cases for Mali.
All coloured points indicate median estimates and associated 95% credible intervals for subnational regions in Mali. A: Mean durations of ITN use (hollow) and retention (filled) are shown in addition to national median estimates (black solid and dashed lines, respectively). B: Mean ITN retention and use given access under a triennial campaign strategy are shown, with black lines indicating national median estimates. C: Points indicate mean annual clinical cases under a triennial pyrethroid–PBO campaign strategy, and the projected change in cases for alternative intervention strategies with pyrethroid-only (C.i–iii) pyrethroid-PBO (C.iv–vi) or pyrethroid–chlorfenapyr (C.vii–ix) ITNs, with continuous-only distribution (C.i, iv, vii), or in conjunction with triennial (C.ii, v, viii) or biennial (C.iii, vi, ix) campaigns. The change in clinical cases is equal to zero for equivalent comparator and intervention strategies (C.v). Labeled diagonal reference lines with positive gradients indicate percentage increases in clinical cases relative to mean annual estimates under the comparator strategy; lines of the same style with negative gradients indicate equivalent percentage decreases. Urban areas were estimated to broadly have lower use given access than in rural settings, while the capital city, Bamako, was estimated to have the lowest ITN retention time of all regions. Figure 5—figure supplement 1. Retention time, use given access and changes in cases for Burkina Faso. Figure 5—figure supplement 2. Retention time, use given access, and changes in cases for Ghana. Figure 5—figure supplement 3. Retention time and use given access for Malawi. Figure 5—figure supplement 4. Retention time, use given access and changes in cases for Mozambique. Figure 5—figure supplement 5. Retention time, use given access and changes in cases for Senegal.
Change in cases vs. cases with triennial pyrethroid-PBO distribution.
Points represent urban and rural areas within each subnational region, are colored by country, and are sized proportionally to the mean annual number of ITNs distributed under each strategy. Each point shows median estimates of the change in clinical cases following a switch from triennial pyrethroid-PBO distribution to alternative strategies against the projected clinical cases under the triennial pyrethroid-PBO strategy. Concurrent distribution of continuous ITNs of the same class used in mass campaigns in assumed throughout. Vertical and horizontal lines indicate 95% credible intervals. Labeled diagonal reference lines with positive gradients indicate percentage increases in clinical cases relative to mean annual estimates under the comparator strategy; corresponding lines with negative gradients represent equivalent percentage decreases and share the same line style. Figure 6—figure supplement 1. Change in cases vs. cases with triennial pyrethroid-chlorfenapyr distribution. Figure 6—figure supplement 2. Cases averted under different ITN distribution strategies. Figure 6—figure supplement 3. Change in cases vs Pf PR with triennial pyrethroid-PBO distribution. Figure 6—figure supplement 4. Change in cases vs pyrethroid resistance. Figure 6—figure supplement 5. Change in cases vs duration of use. Figure 6—figure supplement 6. Change in cases vs retention time. Figure 6—figure supplement 7. Change in cases vs use. Figure 6—figure supplement 8. Change in cases vs access. Figure 6—figure supplement 9. Change in cases vs use given access.
An illustration of the number of nets, n(t), in a region over time with continuous replenishment of routinely distributed nets, nd, where nets are distributed every Δt years through regular mass campaigns (solid black lines).
The contribution towards the total number of nets from routine distribution and previous mass campaigns are shown by the dashed and dotted blue lines, respectively. The timing of DHS surveys are shown by the red vertical dashed lines for both regular (left) and irregular (right) surveying.
Posterior predictive distributions (red) from the hierarchical model for the age of a used net in months if one is sampled randomly over time and across either sub-Saharan Africa (a), or within an exemplar country (b) or subnational region (c).
The shaded regions indicate 95% credible intervals, while the blue lines indicate the normalised empirical densities; these were generated from the pseudo-counts as described in equation (4). The peaks at 12, 24 and 36 months in the empirical densities are believed to be artifacts from the survey data due to individuals rounding reported ITN ages to the nearest whole year.
Estimates of mass campaign timings in the subnational Est region in Burkina Faso.
Letting region i be the Est region of Burkina Faso, (a) shows the empirical, Zζ(i), and smoothened, Ƶζ (i), annual numbers of nets delivered nationally are shown by the solid blue line (as reported by the Alliance of Malaria Prevention, AMP) and shaded region. The local minima of Ƶζ (i), which define the midpoints between net delivery dates are shown by the vertical black lines in (a) and (d) and indicate the assumed periods when mass campaigns are allowed to have occurred. The density proportional to the the number of nets received subnationally by month, Xi, is shown in red (b). The weighted version of this density, Wi, to account for older nets being under-represented in DHS surveys is shown in yellow (c). The composite density, Vi, and its smoothened counterpart, 𝒱i, which are constructed from the stepwise densities in (a) and (c) are shown by the green line and shaded region in (d). The densities, 𝒴ik, are subsetted from 𝒱i by the black lines. These are treated as approximations of the probability of a mass campaign occurring in each month, and the expected value for the timing of each kth mass campaign are shown by the black triangles.
Use, access and Pf PR over time in rural Senegal.
Model estimates in a lower transmission context in Senegal are shown. All features remain unchanged from figure 1. Note, in B, some credible intervals extend beyond the y-axis limits, which have been restricted to 30% to aid visibility.
Use of ITNs from continuous channels.
For each subnational region, coloured points indicate median estimates of the mean use of any ITN, and of those sourced from continuous channels, immediately following a mass campaign (A) and over the subsequent three years (B) with associated 95% credible intervals. For each country, the proportion of ITNs that were used which were sourced from continuous channels immediately following a campaign (A) and over the subsequent three years (B) can be estimated from the slopes of the coloured population-weighted linear regression lines, which assume a zero intercept. Estimates over all countries are shown by the population-weighted linear regression line in black.
Mean urban use and access with three-year campaigns.
Central estimates of mean overall proportion of people using an ITN the previous night, access to an ITN, and use given access for three-year mass campaign intervals are shown in the top three rows. The number of months following a mass campaign where overall ITN use exceeds 80% are shown in the bottom row.
Mean rural use and access with two-year campaigns.
Central estimates of mean overall subnational ITN use, access and use given access for two-year mass campaign intervals in rural areas are shown in the top three rows. The number of months following a mass campaign where overall ITN use exceeds 80% are shown in the bottom row.
Mean urban use and access with two-year campaigns.
Central estimates of mean overall subnational ITN use, access and use given access for two-year mass campaign intervals in urban areas are shown in the top three rows. The number of months following a mass campaign where overall ITN use exceeds 80% are shown in the bottom row.
Retention time, use given access, and changes in cases for Ghana.
All features remain unchanged from figure 5. In 2019, several administrative regions in Ghana were subdivided: Brong-Ahafo became Bono, Bono East, and Ahafo; the Northern Region was split into Northern, Savannah, and North East; and Volta was divided into Volta and Oti. Retrospective analyses (A-B) were conducted using the pre-2019 regional boundaries, while future projections (C) used the post-2019 subdivisions. In all subnational regions, ITN retention times and use given access were estimated to be higher in rural than in urban settings.
Retention time and use given access for Malawi.
All features remain unchanged from figure 5.A. Clinical case projections were not conducted for Malawi due to the lack of intervention data stratified to the administrative-one level, despite DHS surveys being conducted at that scale.
Retention time, use given access and changes in cases for Mozambique.
Retention time, use given access and changes in cases for Senegal.
All features remain unchanged from figure 5. While use given access was estimated to be broadly similar across urban and rural settings, ITNs were generally estimated to be retained for longer in rural areas;
Change in cases vs cases with triennial pyrethroidchlorfenapyr distribution.
Points show median estimates of the change in clinical cases following a switch from triennial pyrethroid-chlorfenapyr distribution to alternative strategies against projected clinical cases under the triennial pyrethroid-chlorfenapyr strategy. Figure features otherwise remain unchanged from figure 6.
Projected cases averted under different ITN distribution strategies.
Points indicate median estimates of the mean annual clinical cases averted by different ITN distribution strategies, in comparison to ceasing ITN distribution entirely, against clinical cases under a triennial pyrethroid–PBO distribution strategy. Figure features otherwise remain unchanged from figure 6.
Change in cases vs Pf PR with triennial pyrethroid-PBO distribution.
Points show median estimates of the change in clinical cases following a switch from triennial pyrethroid-PBO distribution to alternative strategies against all-age Pf PR under the triennial pyrethroid-PBO strategy. Figure features otherwise remain unchanged from figure 6.
Change in cases vs pyrethroid resistance.
Points show median estimates of the change in clinical cases following a switch from triennial pyrethroid-PBO distribution to alternative strategies against pyrethroid resistance. Figure features otherwise remain unchanged from figure 6.
Change in cases vs duration of use.
Points show median estimates of the change in clinical cases following a switch from triennial pyrethroid-PBO distribution to alternative strategies against mean duration of use. Figure features otherwise remain unchanged from figure 6.
Change in cases vs retention time.
Points show median estimates of the change in clinical cases following a switch from triennial pyrethroid-PBO distribution to alternative strategies against mean retention time. Figure features otherwise remain unchanged from figure 6.
Change in cases vs use.
Points show median estimates of the change in clinical cases following a switch from triennial pyrethroid-PBO distribution to alternative strategies against mean use over any triennial distribution strategy. Figure features otherwise remain unchanged from figure 6.
Change in cases vs access.
Points show median estimates of the change in clinical cases following a switch from triennial pyrethroid-PBO distribution to alternative strategies against mean access over any triennial distribution strategy. Figure features otherwise remain unchanged from figure 6.
Change in cases vs use given access.
Points show median estimates of the change in clinical cases following a switch from triennial pyrethroid-PBO distribution to alternative strategies against mean use given access over any triennial distribution strategy. Figure features otherwise remain unchanged from figure 6.
