Safety monitoring in vaccine development and immunization.

The development of vaccines has been one of the most important achievement in preventive medicine. As the incidence of vaccine-preventable diseases is reduced by immunization, general public becomes increasingly concerned about the safety associated with vaccine. Vaccine safety is extensively evaluated through animal safety studies, clinical trials, during manufacturing processes, and postlicensure surveillance. Safety monitoring in postlicensure surveillance has relied on passive reporting system and epidemiological studies, including Vaccine Adverse Event Reporting System (VARES), Vaccine Safety Datalink (VSD) Project and others. Approximately 10,000 reports per year are submitted to VAERS. About 15% of these describe serious events and 85% of reports are classified as not-serious events. The system analyzed frequently reported adverse reactions, rare events, intussusception after rotavirus vaccine, cases of sudden infant death syndrome (SIDS), and safety of various vaccines. The evidence for a causal relationship with vaccines can be classified into five categories: no evidence, evidence was inadequate to accept or reject, evidence favors rejection, evidence favors a causal relationship, and evidence established. Future challenges involve improving survey and monitoring system of adverse events after immunization, enhancing vaccine safety research and vaccine risk communication, and possibility of increased reactogenicity in new and combined vaccines.