Bell's Palsy Following SARS-CoV-2 Vaccines: A Systematic Review and Meta-Analysis (preprint)

ABSTRACT

Background and Objective Bell's palsy (BP) has been considered as a serious adverse event following the SARS-CoV-2 vaccination. Many studies have reported BP following vaccination, although neither a causative relationship nor a prevalence of the condition higher than the general population has been established. The outcomes of interest were to compare BP incidence among (a) SARS-CoV-2 vaccine recipients, (b) nonrecipients in the placebo or unvaccinated cohorts, (c) different types of SARS-CoV-2 vaccines, and (d) SARS-CoV-2 infected vs. SARS-CoV-2 vaccinated individuals. Methods We performed a systematic search through MEDLINE (via PubMed), Web of Science, Scopus, Cochrane library, and Google Scholar from the inception to August 15, 2022. We included articles reporting individuals receiving any SARS-CoV-2 vaccine in whom BP had occurred. Studies reporting facial paralysis due to etiologies other than BP were excluded. Random- and fixed-effects meta-analyses using the Mantel-Haenszel method were conducted for the quantitative synthesis. Newcastle-Ottawa scale (NOS) was used to assess the quality. The study was conducted in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline, and the protocol was registered with PROSPERO (CRD42022313299). Analyses were carried out using the R, version 4.2.1 (R package 'meta' version 5.2-0). Results Fifty studies were included, of which 17 entered the quantitative synthesis. First, pooling four phase-3 randomized controlled trials (RCT) indicated BP occurrence was significantly higher in SARS-CoV-2 vaccines (77, 525 doses) compared to placebo (66, 682 doses) (OR = 3.00, 95% CI = 1.10 - 8.18, I2 = 0%). Second, pooling nine observational studies of mRNA SARS-CoV-2 vaccine doses (13, 518,026) and matched unvaccinated individuals (13, 510,701) revealed no significant increase in the odds of BP in the vaccinated group compared to the unvaccinated group (OR 0.70 (95% CI 0.42-1.16), I2=94%). The third meta-analysis suggested that post-vaccination BP among first dose Pfizer/BioNTech recipients (22,760,698) did not significantly differ from that in first dose Oxford/AstraZeneca recipients (22,978,880) (OR = 0.97, 95% CI = 0.82 - 1.15, I2 = 0%). According to the fourth meta-analysis, BP was significantly more commonly reported after SARS-CoV-2 infection (2,641,398) than after SARS-CoV-2 vaccinations (36,988,718) (RR = 4.03, 95% CI = 1.78 - 9.12, I2 = 96%). Conclusion Our meta-analysis suggests a higher incidence of BP among vaccinated vs. placebo groups. BP occurrence did not significantly differ between Pfizer/BioNTech and Oxford/AstraZeneca vaccines. SARS-CoV-2 infection posed a significantly greater risk for BP than SARS-CoV-2 vaccines.