A high-pressure mercury vapor lamp suitable for sterilization purposes. Germanium and oxygen are added in small quantities to the mercury and/or the mercury halides, with a molar ratio of germanium to oxygen being greater than 1. The addition of germanium monoxide increases the GAC efficiency (GAC: short for Germicidal Action Curve) of a high-pressure mercury vapor lamp, because germanium monoxide emits a strong molecular band system in the range from 250 to 280 nm.