A potential signal of Bell's palsy after parenteral inactivated influenza vaccines: reports to the Vaccine Adverse Event Reporting System (VAERS)--United States, 1991-2001

Abstract

Purpose: Post-licensure experience with a new intranasal inactivated influenza vaccine in Switzerland recently identified an increased risk for Bell's palsy. We reviewed reports in the Vaccine Adverse Event Reporting System (VAERS) to assess if parenteral inactivated influenza vaccines (influenza vaccines) may also increase the risk for Bell's palsy.

Methods: Reports of Bell's palsy after influenza vaccines in VAERS from 1/1/1991 to 12/31/2001 were identified by searching the Coding Symbols for Thesaurus of Adverse Reaction Terms (COSTART) for 'paralysis facial' and by text string search in the automated database. The text descriptions on each report were reviewed to verify the diagnosis. The proportional reporting ratio (PRR) was calculated to aid signal detection.

Results: We found a total of 197 reports of Bell's palsy after receipt of influenza vaccines. The diagnosis was verified for 154 (78.2%), of which 145 (94.2%) had received influenza vaccines alone. The verified reports were submitted from 35 states; 58% of the reports involved persons living in states where the risk of Lyme disease, which can also cause facial paralysis, was low, minimal or none. The PRRs in all age groups exceeded the criteria for a signal of possible association. The highest PRR was 3.91 in the > or = 65 years age group.

Conclusions: Our findings revealed a signal of possible association between influenza vaccines and an increased risk of Bell's palsy. A population-based controlled study is needed to determine whether this association could be causal and to quantify the risk.