On the “Take” as a Biomarker

Arguably the best biomarker in the world for vaccine efficacy is the “take.” The take, the reaction observed after an inoculation of smallpox vaccine, is typically a small pustular lesion that occurs approximately 1 week after inoculation and often leaves a poxlike scar at the vaccination site. This reaction allows health care personnel to know that a person is immune to variola and that the immunity is long-lasting. This simple observation, which was reported by Edward Jenner in the late 1700s and could be recognized by anyone anywhere in the world, contributed enormously to the eradication of the disease, with . . .