Initial case was retrieved from the scientific literature on 23 February 2012. Verbatim from report: "Abstract In fall 2010, an increased risk of febrile seizures was noted in young children in the 24 h after receipt of influenza vaccine manufactured by CSL Biotherapies. Although the CSL TIV vaccine was not recommended for use in young children, during the 2010-2011 influenza season near real-time surveillance was conducted for febrile seizures in the 0-1 days following first dose TIV in a cohort of 206,174 vaccinated children ages 6 through 59 months in a project. On a weekly basis, surveillance was conducted with the primary approach of a self-controlled risk interval design and the secondary approach of a current vs. historical vaccine design. Sequential statistical methods were employed to account for repeated analysis of accumulating data. Signals for seizures based on computerized data were identified in mid November 2010 using a current vs. historical design and in late December 2010 using a self-controlled risk interval design. Further signal evaluation was conducted with chart-confirmed febrile seizure cases using only data from the primary approach (i.e. self-controlled risk interval design). The magnitude of the incidence rate ratio and risk difference comparing risk of seizures in the 0-1 days vs. 14-20 days following TIV differed by receipt of concomitant PREVNAR 13. Among children 6-59 months of age, the incidence rate ratio (IRR) for TIV adjusted for concomitant PREVNAR 13 was 2.4 (95% CI 1.2, 4.7) while the IRR for PREVNAR 13 adjusted for concomitant TIV was 2.5 (95% CT 1.3, 4.7). The IRR for concomitant TIV and PREVNAR 13 was 5.9 (95% CI 3.1, 11.3). Risk difference estimates varied by age duet to the varying baseline risk for seizures in young children, with the highest estimates occurring at 16 months (12.5 per 100,000 doses for TIV without concomitant PREVNAR 13, 13.7 per 100,000 doses for PREVNAR 13 without concomitant TIV, and 44.9 per 100,000 doses for concomitant TIV and PREVNAR 13) and the lowest estimates occurring at 59 months (1.1 per 100,000 doses for TIV without concomitant PREVNAR 13, 1.2 per 100,000 doses for PREVNAR 13 without concomitant TIV, and 4.0 per 100,000 doses for concomitant TIV and PREVNAR 13). Incidence rate ratio and risk difference estimates were lower for children receiving TIV without concomitant PREVNAR 13 or PREVNAR 13 without concomitant TIV. Because of the importance of preventing influenza and pneumococcal infections and associated complications, our findings should be placed in a benefit-risk framework to ensure that population health benefits are maximized. Results Signal identification From August 1, 2010 to February 5, 2011, first dose TIV was administered to 206,174 children ages 6-59 months and to 384,098 children ages 5-17 years. During the week of November 14, 2010 in the third week of surveillance, a statistical signal for seizures in children 6-59 months was identified using the current vs. historical CMaxSPRT approach, corresponding to a relative risk of 3.3 based on 12 observed vs. 3.6 expected cases. Six weeks later, during the week of December 26, 2010, a statistical signal was also detected in children ages 6-59 months using the self-controlled risk interval binomial-based MaxSPRT approach, with a relative risk of 5.7 based on 17 cases in the 0-1 day risk interval and 3 cases in the 14-15 day control interval. No statistical signals were identified for children ages 5-17 years during surveillance. Medical record reviews A total of 32 potential cases in the risk interval (i.e. 0-1 days) and 34 potential cases in the control interval (i.e. 14-20 days) were identified in computerized data. Of the 30 potential cases in the risk interval that had medical records available for review, 27 (90%) cases met Brighton criteria level 1 (n = 2) or VSD criteria levels 4A (n = 1), 4B (n = 3), 4C (n = 7), or 4D (n = 14) for generalized seizures following TIV. Twenty-five seizure cases (83%) in the risk interval were categorized as having a febrile seizure, though only 21 (70%) met the Brighton criterion for documented fever of > or = 38 degree C. Additional clinical characteristics of chart confirmed cases in the risk and control intervals are described. Of the 31 potential cases available for review in the control interval, 26 (84%) met Brighton criteria level 1 (n = 2) or VSD criteria levels 4A (n = 1), 4B (n = 5), 4C (n = 7), or 4D (n = 11), 22 (71%) also had associated fever, and 20 (65%) met the Brighton criterion for fever. The 25 and 22 chart confirmed febrile seizure cases that had occurred in the risk and control intervals following TIV were included in all regression models." The outcome was not reported. Documents held by sender: None.