Case-centered analysis results of Guillain-Barré syndrome (GBS) with prior vaccination and with prior infection, Vaccine Safety Datalink, 2009–2011.

aAdjusted for GBS onset date, age group, sex, site, and medically-attended infection status in 1 through 42 days prior to GBS onset.bAdjusted for GBS onset date, age group, sex, site, and influenza vaccination status (2009–10 monovalent inactivated influenza vaccine or 2010–11 trivalent inactivated influenza vaccine) in 1 through 42 days prior to GBS onset.cMedically-attended infection definitions: A. Respiratory tract, acute gastrointestinal, or unspecified viral infection; B. Respiratory tract including influenza; C. Influenza; D. Respiratory tract with fever and/or influenza or respiratory syncytial virus lab test ordered on same day; E. Respiratory tract with fever and/or positive influenza or respiratory syncytial virus lab test on same day; F. Acute gastrointestinal; G. Acute gastrointestinal and/or diarrhea.dThe prior VSD GBS study reported 9 cases in the risk interval and 4 cases in the control interval following 2009–10 MIV [15]. One vaccinated GBS case in the risk interval was uninformative in case-centered analysis (100% probability of being in risk interval), so 8 are reported here. There are 5 cases in the control interval for this study because 1 case was dropped (onset occurred within the newly established 43 through 49 day washout interval) while 2 cases were gained (1 case from an additional VSD site added for this study, and 1 case newly identified at a VSD site included in the prior study).eA post-hoc analysis restricting to cases with antecedent 2009–10 monovalent inactivated influenza vaccine and no adjustment for infection status yielded a point estimate slightly further from the null (odds ratio = 2.10, 95% CI: 0.54–8.22).fA post-hoc analysis restricting to cases with antecedent 2010–11 seasonal trivalent inactivated influenza vaccine and no adjustment for infection status yielded a point estimate slightly further from the null (odds ratio = 1.25, 95% CI: 0.30–5.29).gAlthough analysis 13 had the same control interval definition as analysis 12 (days 50–126), analysis 13 had one fewer case in the control interval (17 vs. 18). This is because cases are only informative if they have a nonzero probability of being in either the risk or control intervals. The dropped case occurred in April 2011, with a 0.8% probability of being exposed in the 1 through 42 day risk interval in analysis 12, but a 0% probability of being exposed in the 1 through 21 day risk interval in analysis 13.