Bell palsy following intranasal vaccination
Results from a case–control study and a case-series analysis indicate a significantly increased risk of Bell palsy developing following intranasal immunization with a new vaccine. This inactivated influenza vaccine, composed of influenza antigens in a virosomal formulation with E. coliderived LT adjuvant, was licensed in Switzerland in October 2000. Following spontaneous reports of Bell palsy, the company decided not to market the vaccine during the following season.
In general, the etiology and pathogenesis of Bell palsy remain inadequately understood. The greater risk of Bell palsy following immunization with this vaccine may be due to specific vaccine components such as LT toxin, influenza antigens or virosomes, or simply to use of the intranasal administration route. It is thus possible that such complications of vaccine administration may also apply to other nasal vaccines. GACVS therefore recommends that any novel vaccine for nasal administration should be tested on a sufficiently large number of subjects before licensing and submitted to active post-marketing surveillance studies. Since the average time to onset of Bell palsy following intranasal immunization with this new vaccine was as much as 60–90 days, GACVS recommends that the follow-up period in the context of clinical trials should be routinely extended to 3 months following administration of a new intranasal vaccine.