Featuring articles on hydroxychloroquine for Covid-19 prophylaxis, subcutaneous or transvenous ICD therapy, Zika virus disease in Colombia, ofatumumab vs. teriflunomide in multiple sclerosis, and spending after state specialty-drug out-of-pocket caps; a review article on native-valve infective endocarditis; a Clinical Problem-Solving on being led astray; and Perspective articles on the National Academy of Medicine and the quality of health care, on care churn, on mental health and the Covid-19 pandemic, and on preventing a parallel pandemic. Supplement to the New England Journal of Medicine, Vol. 383, No. 6.