TeleWatch is an automated telephone/Internet-based system that collects medical product adverse event reports in real-time through an algorithm driven by the patient. 1341 patients, who received yellow fever vaccine and were recruited through 15 travel clinics, contacted the system within 48h of vaccination and 765 (57%) made follow-up contacts. Participation rates were higher among females and persons older than 60 years of age. TeleWatch can be expanded for use in large campaigns involving influenza or other vaccines.