Bell's palsy and SARS-CoV-2 vaccines—an unfolding story
Authors: Nicola Cirillo, Richard Doan
Journal: The Lancet Infectious Diseases (2021)

Following the documentation of a case of Bell's palsy associated with vaccination,1Colella G Orlandi M Cirillo N Bell's palsy following COVID-19 vaccination.J Neurol. 2021; (https://dx.doi.org/10.1007%2Fs00415-021-10462-4 published online Feb 21.)Crossref PubMed Scopus (61) Google Scholar 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 colleagues2Ozonoff A Nanishi E Levy O Bell's palsy and SARS-CoV-2 vaccines.Lancet Infect Dis. 2021; 21: 450-452Summary Full Text Full Text PDF PubMed Scopus (107) Google Scholar 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,3Victor M Martin J Disorders of the cranial nerves.in: Isselbacher KJ Harrison's principles of internal medicine. 13th edn. McGraw-Hill, New York, NY1994: 2347-2352Google Scholar, 4Erdur H Ernst S Ahmadi M et al.Evidence for seasonal variation of Bell's palsy in Germany.Neuroepidemiology. 2018; 51: 128-130Crossref PubMed Scopus (9) Google Scholar the generally agreed incidence of Bell's palsy is 15–30 cases each year per 100 000 population. Ozonoff and colleagues2Ozonoff A Nanishi E Levy O Bell's palsy and SARS-CoV-2 vaccines.Lancet Infect Dis. 2021; 21: 450-452Summary Full Text Full Text PDF PubMed Scopus (107) Google Scholar 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).TableExpected and actual rates of Bell's palsy in COVID-19 mRNA vaccine trialsExpected occurrence during mRNA vaccine trials (recipients)Actual occurrence during mRNA vaccine trials (recipients)Actual occurrence during mRNA vaccine trials (doses)Rate per 100 000*Rate per 100 000 recipients for the second and third columns and per 100 000 doses for the fourth column.∼3 to 7 cases (15–30 cases per year)∼21 cases (89 cases per year)∼10 cases (44 cases per year)Ratio1:14 285 to 1:28 5701:50001:10 000* Rate per 100 000 recipients for the second and third columns and per 100 000 doses for the fourth column. Open table in a new tab 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. Bell's palsy and SARS-CoV-2 vaccinesIn light of the ongoing pandemic, development of vaccines to protect against SARS-CoV-2 infection and COVID-19 disease is an important public health priority. As of February 2021, two SARS-CoV-2 vaccines have received emergency use authorisation by the US Food and Drug Administration (FDA), both of which use mRNA technology. While the safety data are reassuring, phase 3 studies of both vaccines demonstrate an imbalance of cases of Bell's palsy in the vaccine groups compared with the placebo groups. Full-Text PDF Bell's palsy and SARS-CoV-2 vaccines—an unfolding story – Authors' replyWe thank Nicola Cirillo and Richard Doan for their careful consideration of our Comment1 and the available safety data from the recent mRNA vaccine trials. They are correct to call attention to the follow-up period for reporting safety events as important to interpret event rates appropriately. We have three points in response. Full-Text PDF