Facial Paralysis Following Influenza Vaccination: A Disproportionality Analysis Using the Vaccine Adverse Event Reporting System Database

Background and Objective Several cases of facial paralysis have been reported following influenza vaccination; however, recent surveillance studies have not shown an increased risk. In this study, we analyzed the vaccine adverse event reporting system (VAERS) data to determine whether the facial paralysis reporting rate is higher in those who received influenza vaccination compared with those who received other vaccines. Methods We evaluated reports of facial paralysis in people who received influenza vaccination during January 2015 to October 2019 using Medical Dictionary for Regulatory Activities Preferred Terms. A disproportionality analysis was performed to determine the proportional reporting ratio (PRR), Chi-square statistic, and reporting odds ratio (ROR) with 95% confidence interval (CI). The demographic and clinical characteristics of the cases were also analyzed. Results Two hundred fifty cases of facial paralysis following influenza vaccination were reported during the study period. The median age of the patients was 45 (interquartile range, 30-57) years; 132 (52.8%) patients were females. The majority of the patients received the injected trivalent or quadrivalent seasonal influenza vaccine by intramuscular route. The PRR, Chi-square statistic, and ROR (95% CI) was 2.44, 122.32, and 2.44 (2.08-2.88), respectively; on excluding cases involving concomitant paresis/paralysis of limbs or Guillain-Barre syndrome, the disproportionality statistics were 2.30, 89.37, and 2.30 (1.93-2.75), respectively. Conclusions Our study shows increased reporting of facial paralysis following influenza vaccination as compared with other vaccines. Considering the inherent limitations of the VAERS database analysis, and the fact that disproportionality measures only indicate the presence of a signal, our study findings need to be explored in well-designed prospective pharmacoepidemiologic studies.