Ban on thiomersal in vaccines would damage global immunization efforts Government representatives are conference in Geneva this week to choose whether to introduce a worldwide ban in mercury that could consist of thiomersal, a mercury-based preservative that is found in some vaccine production since the 1930s to avoid bacterial or fungal contamination of multidose vials of vaccine, Seth Berkley, a medical epidemiologist and leader of the GAVI Alliance, writes in a fresh York Instances opinion piece inability to sustain . Regardless of the ominous connotations of mercury, your choice should in theory be considered a no-brainer: The scientific and medical consensus is usually that thiomersal poses no individual health risk, and that than conserving lives rather, a ban would place an incredible number of the world's poorest children vulnerable to deadly illnesses by disrupting vaccination applications, he continues.