Immunization and Bell's palsy in children: a case-centered analysis.

Bell's palsy (BP) is an acute and idiopathic paralysis of the facial nerve, with an estimated incidence ranging from 11.5 per 100,000 person-years to 53.3 per 100,000 person-years in different populations. BP has been reported following immunization with inactivated trivalent influenza vaccine (TIV) and hepatitis B virus (HBV) vaccine. Epidemiologic studies examining this association among children are lacking. From 2001 through 2006, all children aged ≤18 years diagnosed with BP within the Kaiser Permanente Northern California population were identified using International Classification of Diseases, Ninth Revision, code 351.0. All electronically identified cases were reviewed and adjudicated by an otolaryngologist (n = 233). Using a case-centered approach, the authors examined the risk of BP during 3 risk intervals. Immunization with TIV (odds ratio (OR) = 0.7, 95% confidence interval (CI): 0.2, 2.8), HBV vaccine (OR = 0.8, 95% CI: 0.2, 2.4), or any vaccine (treating all vaccines combined; OR = 0.9, 95% CI: 0.6, 1.4) was not associated with increased risk of BP 1-28 days after immunization. Similarly, no association was found between vaccines and BP during the periods 1-14 and 29-56 days following immunization. Results of this study suggest that there is no association between immunization and BP in children.