Bell's Palsy and COVID-19 Vaccination: A Systematic Review

Background: Bell's palsy is a rare adverse event reported in COVID-19 vaccines. Given the importance of neurological manifestations, the necessity to highlight and scrutinize the incidence of them following COVID-19 vaccination is needed. This study aimed to systematically review the reported cases of Bell's palsy following vaccination against COVID-19. Methods: This systematic review is conducted based on the Cochrane Collaboration Handbook and PRISMA Statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyzes) and using the Joanna Briggs Institute (JBI) methodology for systematic reviews. The inclusion criteria for the included published studies were patient age ≥18 years, history of Bell's palsy after COVID-19 vaccination and established diagnosis in the patients with COVID-19 vaccination. The exclusion criteria were repeated cases and missing clinical information. The search strategy aimed to find both published and unpublished studies in August 2021 and updated by hand searching in May 2022 using the identified keywords and index terms in Cochrane Library, MEDLINE (PubMed), Web of Science, Scopus, ProQuest, and Google scholar. Finally, the reference lists of all identified reports and articles were searched for additional studies. The JBI critical appraisal tools for case reports or case series were used to assess the risk of bias in the included studies. Results: During the electronic search, hand search, and reference check, we identified 1281 citations, and in hand searching, we detected additional 15 studies. After omitting duplicated citations and assessing the title, abstract, and full text 15 case-report and two case-series studies were included for the critical appraisal process and were included in this study. Pfizer and Moderna vaccines were the most common vaccines among articles that reported the cases of Bell’s palsy. Left-sided paralysis was more common than right-sided paralysis. The interval between receiving the vaccine and the onset of facial weakness was between 1 and 48 days. Conclusion: Further studies with larger sample sizes are necessary to assess the association between Bell's palsy and the dose-response of the COVID-19 vaccine.