Bell’s palsy is an acute idiopathic lower motor neuron facial palsy. Although the cause of Bell’s palsy is unclear, it is believed that the mechanism of the lower motor neuron lesion is related to facial nerve inflammation and edema linked to a virus [1] . The facial asymmetry can cause acute impairment by affecting their facial expression and ability to eat and drink [1] . As Bell’s palsy is a temporary impairment, the majority of patients (up to 70%) will recover without treatment in 6 weeks while 90% of cases are completely resolved with corticosteroid treatment by 9 months [2] . However long-term complications of in-complete recovery of facial weakness can lead to significant morbidity, as well as anxiety and distress [1] .

Previously there was increased incidence of Bell’s palsy after receiving influenza and meningococcal vaccine. However, the significant causal link has not been established [1] . Similar occurrences of unilateral facial palsy have been reported in the event of COVID-19 vaccination. Several cases reported of Bell’s palsy after receiving Pfizer/BioNTech (BNT162b2), Moderna, CoronaVac (Sinovac) and Oxford/AstraZeneca vaccines [1] [3] [4] .

Patient safety and vaccine efficacy were prime concerns to achieve comprehensive vaccination coverage in a short period. The National COVID-19 Immunization Programme ensured a safe and effective vaccination to combat the pandemic. Our government has adopted a systematic approach to its vaccine acquisition efforts through diplomatic relations and strategic international cooperation with other countries, manufacturers, world health bodies, and affiliates. We aimed to review COVID-19 vaccines-related Bell’s palsy and the essential characteristics of COVID-19 vaccine recipients in Malaysia. These will serve as relevant information for a future pandemic and thus assist healthcare front liners in making vaccination decisions, particularly for high-risk groups.

As the Bell’s palsy requires prompt evaluation of the head and neck region, most cases in Hospital Kuala Lumpur are referred and managed by ENT team. Here we would like to share our experience in Hospital Kuala Lumpur regarding Bell’s palsy post COVID-19 vaccination.

A retrospective cross-sectional study at the Otorhinolaryngology (ORL) outpatient department of Hospital Kuala Lumpur, Malaysia between 1^st May 2021 and 30^th November 2021. The diagnosis of Bell’s palsy was confirmed clinically. A total of 26 cases of Bell’s palsy data were collected from health record data. Inclusion criteria include Bell’s palsy onset within 60 days either after the first or the second vaccine dose with complete data from clinical records. A Cerebral Vascular Accident (CVA), Ramsay Hunt syndrome, history of Bell’s palsy, and age below 18 were excluded. All baseline characteristics of the patient, clinical history and history of vaccination were collected. The facial paralysis was graded according to the House-Brackmann grading system [5] , in which.

Grade 1: Normal—Normal facial function in all areas

Grade 2: Mild dysfunction

Gross: Slight weakness noticeable on close inspection; may have very slight synkinesis

At rest: Normal symmetry and tone

Motion

Forehead: Moderate to good function

Eye: Complete closure with minimum effort

Mouth: Slight asymmetry

Grade 3: Moderate dysfunction

Gross: Obvious but not disfiguring difference between two sides; noticeable but not severe synkinesis, contracture and/or hemifacial spasm

At rest: Normal symmetry and tone

Motion

Forehead: Slight to moderate movement

Eye: Complete closure with effort

Mouth: Slightly weak with maximum effort

Grade 4: Moderately severe dysfunction

Gross: Obvious weakness and/or disfiguring asymmetry at rest: normal symmetry and tone

Motion

Forehead: None Eye: incomplete closure Mouth: asymmetric with maximum effort

Grade 5: Severe dysfunction

Gross: Only barely perceptible motion

At rest: Asymmetry

Motion

Forehead: None

Eye: Incomplete closure

Mouth: Slight movement

Grade 6: Total paralysis

No movement

There is no specific data on Bell’s palsy prevalence locally. Even more, there was no data on inactivated vaccination causing Bell’s palsy locally and internationally. Therefore, assuming 1% based on Bell’s palsy effect following influenza vaccination. By using a universal sampling, all patients were included in the study.

Based on Krejcie and Morgan’s (1970) table for determining sample size, for a given population (N) of 30 with confidence 95% and margin of error (e) 5.0%, a sample size of 28 would be needed to represent a cross-section of the population. However, using a universal sampling, we will collect all the date within the time frame (1^st May 2021 and 30^th November 2021).

A total of 26 patients presented with ipsilateral lower motor neuron facial palsy within 6 months. The age group ranged from 22 to 61 years old, with a mean age of 38.5 years. The majority were in the younger age group; 18 - 30-year-old (n = 11), and the least number was found in older age 60 and more (n = 2). There was equal distribution in gender (n = 13 each). The majority were Malay 80.7% (n = 21) followed by Indian (n = 2), Chinese (n = 2), and Bangladeshi. Most of the patients 76.9% (n = 20) were healthy without any comorbidity. Except only 6 of them have comorbidities.

Further vaccination-related history showed most of the patients 50% (n = 13) presented with Bell’s palsy within the first week after receiving the vaccine. The onset of facial palsy is as early as day 1 to day 47 after vaccination. Equally distribution was observed number of Bell’s palsy after first and second dose vaccine (n = 13 each). We found that Bell’s palsy was quite similar in number; Pfizer vaccine (n = 9), Sinovac (n = 9) and AstraZeneca (n = 8) (summarized in Table 1).

The first vaccination phase in Malaysia was launched in February 2021 and lasted until April 2021. This phase focused on the frontliners in the public and private healthcare sectors, essential services, defense, and security. The second phase was initiated in April 2021 and lasted until August 2021. Apart from maintaining the frontliners, senior citizens (those aged 60 and over), people with chronic diseases (such as heart disease, obesity, diabetes, and high blood pressure), and people with disabilities or special needs were included. The third vaccination phase targeted the adult population, anyone over 18 years old (both citizens and non-citizens) and lasted from 20 May 2021 until 20 February 2022.

We received few types of COVID-19 vaccine from different manufacturing companies including Pfizer-BioNTech (Comirnaty), Sinovac (CoronaVac) and Oxford-AstraZeneca (ChAdOx1-S) [4] . There has been no publication in Malaysia regarding the vaccine side effect of Bell’s palsy yet. A survey on the adverse effects of the COVID-19 vaccination was conducted on 428 vaccinated people. Pain or swelling at the injection site, fatigue, myalgia, and fever were the most common adverse effects [6] while Bell’s palsy is not listed as it is such a rare condition.

So far there is no clear evidence between association between Bell’s palsy and COVID-19 vaccine. There are few hypotheses that can trigger Bell’s palsy. The mRNA-based vaccine is thought to be involved in autoimmune phenomenon by either mimicking the host molecule or bystander activation of dormant autoreactive T cells [7] . It is also can induce innate immune activation and produce interferon proteins by a combined effect of mRNA and lipids. Another possible mechanism is an activation of latent herpes simplex type 1 infections in the geniculate ganglia of facial nerve [8] . While, inactivated vaccine such as Sinovac (CoronaVac) is postulated to affect immune reaction. Inactivated virus is used as

M (male), F (Female), BANG (Bangladeshi), NKMI (Not known any medical illness), DM (diabetes mellitus), HPT (hypertension) HPL (hyperlipideamia), 1^st (1^st dose of vaccination), 2^nd (2^nd dose of vaccination) D (day), AZ (Astra Zeneca).

a vaccine to against viral illness which already well known to have a variety of viral antigens that may affect the immune response in a larger group of patients [2] .

The mRNA-based vaccine such as Pfizer/BioNTech or Moderna is a new type of vaccine in medical history. It is using mRNA molecule to stimulate the immunity by recognizing the targeted virus protein. It is simple and quick to produce thus it is widely used in many parts of the worlds. From 2 clinical trial of these vaccines had reported 7 cases of Bell’s palsy in the vaccinated group of 35,000 patients [4] . The Bell’s palsy was reported as a rare adverse event in the European Medicines Agency approved summary of product characteristic Pfizer and Moderna vaccine [2] . Cirillo and Doan reported the incidence of Bell’s palsy in the mRNA vaccine groups was 1.5 - 3 times higher than expected in general population [9] . In contrast, few studies reported no significant relation of Bell’s palsy and BNT162b2 [10] [11] . In contrast, our data showed 3 major vaccines were no difference in relation to Bell’s palsy.

There is not much published data regarding risk of facial palsy following inactivated vaccine. A case series and nested case control study among Hong Kong population showed increased risk of Bell’s palsy after CoronaVac vaccination. The risk to get facial palsy was similar with previous research done by precious study was 1.5 - 3 times higher following mRNA vaccine [2] .

Side effect of vaccine in general showed higher incidence in female and younger age group that was found in local data [6] . In addition, the side effect of vaccine was observed more after second dose especially Pfizer receiver [6] . Those who received the Sinovac vaccine had lower risk of side effects than Pfizer and Oxford/AstraZeneca receivers [6] .

WHO reported 67.8% female developed facial palsy following mRNA COVID-19 vaccination. In contrast, Wan found higher incidence of Bell’s palsy post CoronaVac vaccination were men (68%). There was no gender difference was observed in recipients of BNT162b2 [2] . Our data showed equal gender distribution developed Bell’s palsy however we found younger people are mostly affected as showed in our data. Patients with Bell’s palsy 92% were younger below 60-year-old. It can be attributed due to age related decline in immune response. Malay was higher incidence as Malay is the largest race in our country. The timing onset of Bell’s palsy were higher 50% within first week of vaccination showed strongly suggest that it may related to vaccine injection in regards of what type of vaccine. We recommend further surveillance and more research in regard of this matter.

There are several limitations, as our data is very small. The number could be underrated as we are not able to get data from patients with Bell’s palsy who went to private clinics and other hospitals. However, as a tertiary hospital in Malaysia, the data might be representative.

In general, Bell’s palsy is a good prognosis. More than 90% of Bell’s palsy cases will be recovered completely within 6 months after prompt corticosteroid treatment [2] . The beneficial effects of the COVID-19 vaccine far outweigh the risk of this generally self-limiting adverse event.

We found that non comorbidities, younger people were mostly affected within the first weeks of vaccination. However, we cannot conclude the vaccine is directly the cause of Bell’s palsy. It is a possible adverse effect. Further studies are needed with a sufficient sample size are needed to evaluate the association between Bell’s palsy and the COVID-19 vaccine.

The authors declare no conflicts of interest regarding the publication of this paper.

Jaafar, R.J., Thuraisingam, K., Yusof, A.N.M. and Hailani, I. (2023) Bell’s Palsy Post COVID-19 Vaccination: A Retrospective Cross-Sectional Study in a Single Tertiary Center. Journal of Biosciences and Medicines, 11, 47-53. https://doi.org/10.4236/jbm.2023.1112005