Vaccines and Bell's palsy: A narrative review.

The association between vaccines and peripheral facial palsy (PFP), an issue that has been the subject of debate for many years, has been raised again following results of clinical trials assessing mRNA based COVID-19 vaccines. To review the available literature on this topic, PubMed was searched from inception until February 25, 2022. Inclusion criteria were case reports with documented rechallenge and comparative epidemiological studies. Cases of COVID-19 vaccine-induced PFP with available data on vaccine rechallenge were also identified from Vigibase until December 31, 2021. Of the 347 articles retrieved, 32 comparative epidemiological studies, 1 meta-analysis and 4 case reports met our criteria, of which 13 involved COVID-19 vaccines. Eight studies found an association between at least one vaccine and the occurrence of PFP, whereas 24 did not. Positive studies involved seasonal or pandemic H1N1 influenza vaccines administered parenterally (4 studies) or intranasally (1 study with a toxin-adjuvanted vaccine), BNT162b2, a mRNA COVID-19 vaccine (1 disproportionality analysis and 1 observed-to-expected analysis) and an inactivated virus COVID-19 vaccine (CoronaVac®) (1 study combining a case-control and an observed-to-expected approach). Strong evidence was found only for the intranasal influenza vaccine while other positive studies detected only a marginal association between PFP and vaccination. Of the four case reports with documented rechallenge, only two were positive and involved an influenza vaccine and tozinameran in one case each. In Vigibase, rechallenge was documented in 49 reports with 29 (59.2%) cases being negative and 20 (40.8%) positive. The available data did not confirm an excess risk of PFP after vaccination in most studies. Moreover, of the eight epidemiological studies suggesting a possible excess risk of PFP after any vaccine, three were disproportionality analyses and two observed-to excepted analyses, suggesting great caution should be taken when interpreting these results.

Guillain-Barré Syndrome Associated with COVID-19 Vaccines: A Perspective From Spontaneous Report Data.

BACKGROUND AND OBJECTIVE: The concern surrounding the association between Guillain-Barré syndrome (GBS) and vaccination has increased with the widespread use of COVID-19 vaccines. The aim of this study was to assess the potential association of GBS with mRNA-based or adenovirus-vectored COVID-19 vaccines. METHODS: Reports of GBS associated with mRNA-based or adenovirus-vectored COVID-19 vaccines were extracted from the WHO pharmacovigilance database, exposure data from the Our World in Data website, and the background rates of GBS from published data. For countries contributing to VigiBase and with available data on COVID-19 vaccine exposure, reporting rates were estimated and observed-to-expected (OE) analyses were performed. RESULTS: A total of 2499 cases were included: 1157 (46.3%) cases with adenovirus-vectored COVID-19 vaccines and 1342 (53.7%) with mRNA-based COVID-19 vaccines. The male-to-female sex ratio was 1.09 and the median (IQR) age was 57 (45-66) years. The reporting rates (95% CI) per 100,000 person-years within the 42-day window were 5.57 (5.13-6.03) for adenovirus-vectored COVID-19 vaccines and 1.39 (1.31-1.47) for mRNA-based COVID-19 vaccines, while the background incidence was 1.2-3.1 per 100,000 person-years. For mRNA-based COVID-19 vaccines, the OE ratio was <1 for both time windows in all European countries and slightly elevated for the 21-day window in the USA. For adenovirus-vectored COVID-19 vaccines, the OE ratio was consistently > 2.0 for all countries. Sensitivity analyses minimally altered these results. CONCLUSIONS: These findings suggest both the absence of safety concern for GBS with mRNA-based COVID-19 vaccines and an increased risk with adenovirus-vectored COVID-19 vaccines. Back to top.