Vaccination-induced transmission of varicella: a 31-year old father became severely ill with varicella nine days after his one-year old son was vaccinated against measles, mumps, rubella and chickenpox with the quadruple vaccine PRIORIX-TETRA. He developed high fever and had to be treated in hospital with antiviral agents (NETZWERK report no. 14.784). Chickenpox is known to be a highly contagious disease. An attenuated live virus strain is used for vaccination; transmission to susceptible contact persons is possible even if the vaccinated person himself remains little affected and only develops a chickenpox-like rash. Infection of siblings, playmates, parents or other contact persons has been documented in association with varicella vaccination. This should be considered particularly when pregnant women or persons with weakened immunity live in the vaccinated person's household. Because of infection with the wild virus in childhood, over 90% of today's adult population are immune to varicella. Non-protected adults often become severely ill. The Robert Koch Institute (RKI) recently reported two fatal outcomes in adults and found that "with the increasing effect of vaccination in childhood ... disease might be manifested more often after childhood" (RKI: Epidem. Bull. 2006; no. 25: 191-2). Adults may therefore be at greater risk in future both through infection with the wild virus and through transmission of vaccine viruses. -ed.