The study authors note that they cannot conclude that there is a causal relationship between the COVID-19 vaccines and any of the individual incidents of Bell palsy reviewed.
For every 100,000 people vaccinated with the inactivated vaccine CoronaVac, an additional 4.8 patients may develop Bell palsy, according to the first large-scale population-based study on the association between SARS-CoV-2 vaccines and this condition, published in The Lancet Infectious Diseases. In the case of the Pfizer-BioNTech vaccine, an additional 2 individuals per 100,000 vaccinated may develop the condition. The investigators concluded that this risk is significantly outweighed by the beneficial and protective effects of the vaccines.
The study analyzed incidents of Bell palsy related to the 2 approved vaccines in Hong Kong—CoronaVac and the Pfizer-BioNTech vaccine. Cases were included if they occurred within 42 days of the administration of that individual’s first or second vaccine dose. The investigators used data from the Hong Kong drug regulatory authority pharmacovigilance system, which includes reports of adverse events (AEs) logged by health professionals throughout the territory.
The investigators identified 28 clinically confirmed cases of Bell palsy among the 451,939 individuals who received at least a first dose of CoronaVac (equivalent to 3.61 cases per 100,000 doses administered) and 16 cases among the 537,205 individuals who received at least a first dose of BNT162b2 (equivalent to 2.04 cases per 100,000 doses administered) between February 23rd, 2021, and May 4th, 2021.
“Our study suggests a small increased risk of Bell’s palsy associated with CoronaVac vaccination,” said Ian Chi Kei Wong, PhD, in a press release. “Nevertheless, Bell’s palsy remains a rare, mostly temporary, adverse event. All evidence to date, from multiple studies, shows that the beneficial and protective effects of the inactivated COVID-19 vaccine far outweigh any risks. Ongoing surveillance, through pharmacovigilance studies such as ours are important to calculate with increasing levels of confidence the risks of rare adverse events.”
The study authors note that they cannot conclude that there is a causal relationship between the COVID-19 vaccines and any of the individual incidents of Bell palsy reviewed by the study. Further, the mechanism by which vaccination can lead to Bell palsy in these rare instances remains unclear.
“From a clinical, patient-oriented perspective, none of the studies published so far provide definitive evidence to inform the choice of a specific vaccine in individuals worldwide with a history of Bell’s palsy,” said Nicola Cirillo, DMD, PhD, and Richard Doan, MD, FRCPC, in a linked comment. “However, the data published by Wan and colleagues do offer valuable information for a rational and informed choice of COVID-19 vaccines for patients in Hong Kong, and for those in countries where both BNT162b2 and CoronaVac are available. While waiting for conclusive evidence on vaccine-associated facial paralysis, one certainty remains: the benefit of getting vaccinated outweighs any possible risk.”
The Lancet Infectious Diseases: Benefits of COVID-19 vaccines far outweigh very rare risk of Bell’s palsy, study confirms [news release]. EurekAlert; August 16, 2021. Accessed August 18, 2021. https://www.eurekalert.org/news-releases/925450