Table 1.

Definition of the four different mechanisms determining the overall level of ITN protection and the equations used for their estimation

	Direct net users	Indirect (community effect) net users and non-users
Barrier	(a) Reduction in EIR due to reduced mosquito blood-feeding rate.	(b) Change in EIR for net users and non-users caused by lower human prevalence resulting from (a). Non-users may experience more bites from mosquitoes repelled away from net users
	Calculated as $\mathrm{control}-A$	Calculated as $A-B$
Additional protection from insecticide	(c) Further reduction in EIR caused by insecticide killing and deterrence of blood-seeking mosquitoes	(d) Further reduction in EIR due to higher mosquito mortality, lower mosquito abundance and lower human prevalence resulting from (c)
	Calculated as $A-C$	Calculated as $B-D-\left(A-C\right)$

The four mechanisms (defined a–d) are described according to their impact on transmission. Direct benefits occur to those using ITNs, whereas indirect benefits act upon everyone in a community where ITNs are in use. The value of each are estimated from a transmission dynamics mathematical model, with the different scenarios (italic upper case letters) refer to model run with different assumptions presented in Fig. 2.