Fig. 5: Sample sizes required to detect a superior response in macrofilaricide-treated compared to ivermectin-treated participants.

Each panel depicts sample sizes (n) required to detect, with 80% power, a statistically significant superior response in the macrofilaricide-treated test group compared to the ivermectin-treated control group in an ivermectin-naïve lower-end mesoendemic setting. Sample sizes are calculated at 6, 12, 18 and 24 months after treatment assuming a 10% loss to follow up per year. Macrofilaricidal efficacy (either 60%, 75% or 90%) corresponds to the percentage of adult Onchocerca volvulus killed within three months of treatment with a macrofilaricidal only macrofilaricide (MOM, left-hand side; panels (a) and (c)) or a macrofilaricidal and microfilaricidal macrofilaricide (MAMM, right-hand side; panels (b) and (d)). The parasitological outcome measures are the arithmetic mean number of microfilariae (mf) per mg of skin (microfilarial intensity, panels (a) and (b)) and the percentage of participants positive for mf (microfilarial positive, panels (c) and (d)), both measured by 2 or 4 skin snips and using an infection eligibility criterion before treatment of either >0 (i.e., presence of mf), >4 or >8 mf/mg of skin. Empty squares correspond to time points when the response in the macrofilaricidal-treated test group is inferior to ivermectin.