Long-term impact of vaccination on the overall contribution to onwards transmission by age groups in the host population in absence of ivermectin treatment.
<p>The green <b>(A)</b>, blue <b>(B)</b> and red <b>(C)</b> lines correspond to, respectively, a pre-control endemicity of 40%, 60%, and 80% microfilarial prevalence. The solid line indicates the baseline age-specific contribution to the annual transmission potential (ATP, no. L3/person/year). This is obtained as the product of multiplying the following factors: age- and sex-specific microfilarial loads; proportion of the population within each corresponding demographic stratum; proportion of blackfly bites taken on each demographic stratum (<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0003938#pntd.0003938.g003" target="_blank">Fig 3A</a>); annual biting rate; and the constraining (negative) density-dependent processes, acting on ingested microfilariae within the blackfly vector and on vector survival, that determine L3 output. The dotted lines correspond to the age-specific contributions to the ATP after 15 years of vaccination. The shaded area illustrates the reduction in contribution to transmission by those aged less than 20 years. Modelling assumptions on the initial vaccine efficacy and vaccine duration are as in <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0003938#pntd.0003938.g004" target="_blank">Fig 4</a>. The increasing contribution to ATP by older age groups is mainly due to women for whom microfilarial load and exposure to blackfly bites increases with age (<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0003938#pntd.0003938.g003" target="_blank">Fig 3</a>).</p
