Risk of Facial Palsy Following COVID-19 Vaccination: A Nationwide Large-Linked Database Study

Background: Despite multiple studies on the risk of facial palsy (FP) following COVID-19 vaccination, the results have been inconclusive, lacking a clear consensus. This variability in findings may be attributed to limited statistical power and heterogeneity among studies.

Objectives: To provide updated evidence using a large-linked database by evaluating the potential association between COVID-19 vaccination and FP.

Methods: We conducted a self-controlled case series study by linking the COVID-19 immunization registry from Korea Disease Control and Prevention Agency with the National Health Information Database from February 2021 to October 2022. We included patients aged ≥ 18 years who received at least one dose of COVID-19 vaccine (BNT162b2, mRNA-1273, ChAdOx1 nCoV-19, and Ad.26.COV2.S) and had an incident FP diagnosis with corticosteroid prescription during the study period. In primary analysis, we compared the risk of FP in the period following vaccination (Days 1 to 28) with a control period, using conditional Poisson regression to estimate the incidence rate ratio (IRR) with 95% confidence interval (CI). In secondary analyses, vaccine-specific risks by different vaccine types and doses have been explored. Subgroup analyses were performed by patients’ characteristics, and sensitivity analyses were conducted by varying risk period, FP case definitions, and excluding individuals with COVID-19 infection.

Results: Among 44,564,345 COVID-19 vaccinated individuals with a total of 129,956,027 doses, 5,211 patients experienced FP in the risk period, corresponding to 4.0 cases per 1 million doses (mean [SD] age, 53.1 [15.9] years; 2,849 [54.7%] male). The overall transient risk of FP increased within 28 days following COVID-19 vaccinations (IRR 1.12, 95% CI 1.09-1.16). The risk of FP was primarily determined by the events that occurred after the first and second doses of vaccines (1.08, 1.04-1.12). The findings were largely consistent across vaccine types, for both homologous (1.14, 1.10-1.19) and heterologous dosing (1.08, 1.01-1.14) as well as mRNA (1.11, 1.07-1.15) and viral vector vaccines (1.37, 1.19-1.59). No significant heterogeneity was observed across sex, age group, insurance type, region, and comorbidities. Sensitivity analyses revealed the robustness of the main results, with a significant risk of FP regardless of COVID-19 infection.

Conclusions: Our study observed a slightly elevated risk of FP following COVID-19 vaccinations. However, given the low absolute risk of FP and its generally mild and manageable nature, this should not discourage patients from receiving vaccines. Instead, a comprehensive evaluation of risk-benefit profile associated with COVID-19 vaccines is warranted.