Long-term impact of vaccination on microfilarial load in the absence of ivermectin treatment.

Abstract

<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 lines indicate the pre-control contribution of each group to the overall microfilarial load, which is the product of multiplying the microfilarial age- and sex specific profiles (<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0003938#pntd.0003938.g003" target="_blank">Fig 3B</a>) times the proportion of hosts in each demographic stratum, i.e. the proportion of hosts in each age and sex group (<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0003938#pntd.0003938.g002" target="_blank">Fig 2</a>). The sum total of the age- and sex-specific contributions yields the overall mean microfilarial load. The dotted lines correspond to the values after 15 years of vaccination. The shaded area illustrates the reduction in microfilarial load in those aged less than 20 years. Modelling assumptions are as follows: a vaccination programme targeting initially 1–5 year olds with continuous vaccination of one year olds after the first year of the programme; an initial prophylactic efficacy against the development of incoming worms of 50%; an initial therapeutic efficacy against skin microfilarial load of 90%; a mean duration of protective and therapeutic effects of 20 years (rate of decay = 0.05 per year) and an 80% coverage of vaccination.</p

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