The manuscript was drafted by the corresponding author. All the authors examined critically, edited, and accepted the manuscript and made the decision to post it for publication. No persons apart from the named authors performed any role in writing the manuscript. All the authors assume responsibility for the accuracy and completeness of the info and for the fidelity of the analysis to the protocol, which is obtainable with the full text of this content at NEJM.org. Participants and Group Allocation The study included adults 65 years of age or older without moderate or severe acute illnesses.The principal evaluation examined the %age of index patients who met this end stage. The secondary efficacy analysis was the same evaluation applied to the index individuals plus all enrolled family members . Safety was assessed on the basis of reported adverse occasions and evaluations for pores and skin, scalp, and ocular discomfort in all patients. Statistical Analysis The target sample in each study was planned to provide a lot more than 90 percent power to detect a difference of 45 %age points between ivermectin and vehicle control in the proportion of individuals with louse-free status on days 2, 8, and 15.