Active surveillance for influenza vaccine adverse events: the integrated vaccine surveillance system

Objectives: We conducted a pilot study of the Integrated Vaccine Surveillance System (IVSS), a novel active surveillance system for monitoring influenza vaccine adverse events that could be used in mass vaccination settings.

Methods: We recruited 605 adult vaccinees from a convenience sample of 12 influenza vaccine clinics conducted by public health departments of two U.S. metropolitan regions. Vaccinees provided daily reports on adverse reactions following immunization (AEFI) using an interactive voice response system (IVR) or the internet for 14 consecutive days following immunization. Followup with nonrespondents was conducted through computer-assisted telephone interviewing (CATI). Data on vaccinee reports were available real-time through a dedicated secure website.

Results: 90% (545) of vaccinees made at least one daily report and 49% (299) reported consecutively for the full 14-day period. 58% (315) used internet, 20% (110) IVR, 6% (31) CATI, and 16% (89) used a combination for daily reports. Of the 545 reporters, 339 (62%) reported one or more AEFI, for a total of 594 AEFIs reported. The majority (505 or 85%) of these AEFIs were mild symptoms.

Conclusions: It is feasible to develop a system to obtain real-time data on vaccine adverse events. Vaccinees are willing to provide daily reports for a considerable time post vaccination. Offering multiple modes of reporting encourages high response rates. Study findings on AEFIs showed that the IVSS was able to exhibit the emerging safety profile of the 2008 seasonal influenza vaccine.