Background:Implementation of onchocerciasis elimination programmes has been delayed in Central Africa because of the risk of ivermectin-related serious adverse events (SAEs) in individuals with high Loa loamicrofilarial densities (MFD). We developed the first statistical models enabling prediction of SAE risk in individuals with a given MFD. Methods:We used individual participant data from two trials conducted in loiasis-onchocerciasis co-endemicareas in Cameroon. among the 10 506 ivermectin-treated subjects included in the analysis, 38 (0¢36%) devel-oped an ivermectin-related SAE. To predict individual-level risk of SAE, we developed mixed multivariatelogistic models including subjects'sex, age, pre-treatment L loa and Mansonella perstans MFDs, and study region. Findings:The models predicted that regardless of sex, about 1% of people with 20 000L loa microfilariae permillilitre of blood (mf/mL), 10% of people with 50 000 mf/mL and about one third of those with 100 000 mf/mL will develop an SAE. For a given MFD, males have a three-fold higher risk of developing an SAE than females. Interpretation:By enabling the prediction of post-ivermectin SAE risk in communities with known distribution of L loa MFDs, our results can guide decisions on the choice of ivermectin-based treatment strategies.They also predict that 37 SAEs were prevented in 2015 by using a Test-and-Treat strategy in the Okola District of Cameroon.Funding:UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases; Institut de Recherche pour le Developpement; Mectizan Donation Program; Bill and Melinda Gates Foundation
