Featuring articles on aspirin dosing in cardiovascular disease, antibiotic therapy for prosthetic joint infection, gene therapy for adenosine deaminase deficiency, a novel microRNA in acute myocarditis, and immediate “kangaroo mother care” of low-birth-weight infants; a review article on somatic mutations in “benign” disease; a case report of a woman with abdominal pain and aortic dilatation; and Perspective articles on the “legal epidemiology” of pandemic control, on a hidden opportunity, and on dilemmas of double consciousness. Supplement to the New England Journal of Medicine, Vol. 384, No. 21.