Surveillance for adverse events following immunization (AEFI) in Switzerland - 1991-2001

In Switzerland, reporting of adverse events following immunization (AEFI) has been mandatory by law since 1988. The goal of this study was a detailed analysis of reported AEFI received by the Swiss Federal Office of Public Health between 1991 and 2001. Overall, 1013 AEFI were reported which translates to 2.7 reports per 100,000 vaccine doses distributed during the study period. Most AEFI were classified as general systemic reactions (47%), followed by local (26%), neurological (16%) and allergic reactions (13%). The majority of all reported AEFI (N=513; 51%) had occurred in individuals 16 years and older. Causal relationship between immunization and AEFI was probable in 91 (10%) of 909 assessable reports and very likely or certain in 194 (21%), the majority of which (88%) were local reactions. Vaccines distributed in Switzerland have proven to be generally safe. Limitations of the passive surveillance system, however, warrant improvements in the future.