Following the documentation of a case of Bell's palsy associated with vaccination,1 we were contacted by patients and colleagues from Canada, Australia, Europe, the UK, and United Arab Emirates. Questions raised were whether mRNA vaccine recipients are at increased risk of developing Bell's palsy, and what to recommend to individuals with a history of Bell's palsy.
In their Comment, Al Ozonoff and colleagues2 considered key statistical and epidemiological aspects of SARS-CoV-2 vaccine trial safety data regarding the onset of facial paralysis. Here, we offer a different interpretation of their findings and statistical consideration of risks associated with mRNA and non-mRNA SARS-CoV-2 vaccines.
Despite geographical and seasonal variations,3, 4 the generally agreed incidence of Bell's palsy is 15–30 cases each year per 100 000 population. Ozonoff and colleagues2 rightly state that the predicted 12-month (annual) incidence of Bell's palsy inferred from mRNA vaccine trials is higher than that reported during the 2-month observation period of these studies. They concluded that the observed incidence of Bell's palsy in the mRNA vaccine arms was 3·5 to seven times higher than expected in the general population. However, safety data were collected for participants with a median follow-up of 2 months after the second dose; therefore, the data refer to an overall observation period of approximately 12 weeks from dose one. Given this, and considering Bell's palsy as the possible outcome of individual doses, the observed incidence in the mRNA vaccine trials would be roughly 1·5 to three times higher than in the general population (table ).
Table.
Expected and actual rates of Bell's palsy in COVID-19 mRNA vaccine trials
| Expected occurrence during mRNA vaccine trials (recipients) | Actual occurrence during mRNA vaccine trials (recipients) | Actual occurrence during mRNA vaccine trials (doses) | |
|---|---|---|---|
| Rate per 100 000* | ∼3 to 7 cases (15–30 cases per year) | ∼21 cases (89 cases per year) | ∼10 cases (44 cases per year) |
| Ratio | 1:14 285 to 1:28 570 | 1:5000 | 1:10 000 |
Rate per 100 000 recipients for the second and third columns and per 100 000 doses for the fourth column.
The numerical imbalance reported with mRNA vaccine trials was not seen in the Oxford-AstraZeneca and Johnson & Johnson phase 3 studies using more traditional virus-based technology. Examination of adverse event data from the Yellow Card scheme in the UK and from the EU EudraVigilance database might help clarify this matter. As of March 21, the Yellow Card-reported frequency of facial paralysis or paresis and facial nerve disorder after any dose was close to 23 per million with the Pfizer-BioNTech vaccine and 13 per million with the Oxford-AstraZeneca vaccine. Excluding reports of facial paralysis cross-listed with cerebrovascular accident, EudraVigilance data indicate a much higher frequency of facial paralysis after the Pfizer-BioNTech vaccine than after the Oxford-AstraZeneca vaccine (497 vs 56 cases or 13·6 vs 4·1 per million doses as of April 3). The risk of developing facial paralysis could be two to three times higher in individuals receiving mRNA vaccines than in those receiving traditional vaccines. These findings should be considered when selecting a vaccine for patients with a history of Bell's palsy.
We declare no competing interests.
References
- 1.Colella G, Orlandi M, Cirillo N. Bell's palsy following COVID-19 vaccination. J Neurol. 2021 doi: 10.1007/s00415-021-10462-4. https://dx.doi.org/10.1007%2Fs00415-021-10462-4 published online Feb 21. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Ozonoff A, Nanishi E, Levy O. Bell's palsy and SARS-CoV-2 vaccines. Lancet Infect Dis. 2021;21:450–452. doi: 10.1016/S1473-3099(21)00076-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Victor M, Martin J. In: Harrison's principles of internal medicine. 13th edn. Isselbacher KJ, editor. McGraw-Hill; New York, NY: 1994. Disorders of the cranial nerves; pp. 2347–2352. [Google Scholar]
- 4.Erdur H, Ernst S, Ahmadi M, et al. Evidence for seasonal variation of Bell's palsy in Germany. Neuroepidemiology. 2018;51:128–130. doi: 10.1159/000492097. [DOI] [PubMed] [Google Scholar]