Risk of Bell's palsy following SARS-CoV-2 infection: a nationwide cohort study

Objectives: Despite some evidence of an increased risk of neurologic symptoms following viral vector COVID-19 vaccine administration, it is unclear whether SARS-CoV-2 infection is associated with Bell's palsy (BP), especially over a long enough follow-up period. Methods: The study population of this nationwide population-based study was derived from the South Korean population, including 11 593 365 and 36 565 099 participants with and without COVID-19, respectively. The Fine and Gray's regression model was utilized to calculate the adjusted subdistribution hazard ratio (aSHR), considering death as a competing risk, to assess the association between SARS-CoV-2 infection and the risk of BP. All participants were followed up from 1 December 2021, until the incident BP, SARS-CoV-2 infection, death, or 31 March 2022. Subgroup analyses were conducted based on participants' vaccination status (completion of the primary series vs. unvaccinated). Results: COVID-19 was associated with an increased risk of BP in all participants (aSHR, 1.24; CI, 1.19–1.29). However, the size of the COVID-19–related BP risk was significantly lower among those who completed the primary series of the COVID-19 vaccine (aSHR, 1.20; 95% CI, 1.15–1.25) compared to those who were unvaccinated (aSHR, 1.84; 95% CI, 1.59–2.12; p for interaction: <0.001). The severity of COVID-19 exhibited a gradual escalation in BP risk for both vaccinated and unvaccinated individuals. Discussion: While both unvaccinated individuals and those who completed the primary series of the COVID-19 vaccine may be at an increased risk of developing BP due to COVID-19, the risk appears to be lower among those who completed the vaccination.