Intranasal flu vaccine
In October 2000, an inactivated intranasal flu vaccine was licensed in Switzerland. Results from a case control study and a case-series analysis indicated a significantly increased risk of Bell's palsy, a one-sided paralysis of facial muscles, developing after intranasal immunization with the vaccine. Following spontaneous reports of Bell's palsy in vaccine recipients, the producer decided not to further market the vaccine.
As a result of the occurrence of Bell's palsy, the Global Advisory Committee on Vaccine Safety (GACVS) recommended additional caution for new intranasal vaccines under development and recommended that the follow-up period in the context of clinical trials should be routinely extended to three months following administration.
In 2003, a cold attenuated reassortant live intranasal vaccine was licensed in the US. This vaccine differs in formulation and manufacturing from adjuvanted inactivated intranasal vaccine. Bell's palsy was not observed in clinical trials of the cold attenuated reassortant live intranasal vaccine. As of 6 July 2006, with over four million vaccine doses distributed, a total of five Bell's palsy cases have been reported to the adverse event reporting system of the US. A causal association between these reported cases and the vaccine has not been established.
The GACVS continues to review the safety of vaccines administered by the intranasal route.