Hong Kong, Aug 17 (IANS): The risk of rare Bell's palsy after taking Pfizer's Covid vaccination is very less, finds a study published in The Lancet Infectious Diseases journal, suggesting that the protective effects of the vaccines far outweigh the risk.

Bell's palsy is the sudden onset of one-sided facial paralysis. In the majority of cases (70 per cent), the condition resolves itself within six months without treatment and the chance of recovery is even higher (90 per cent) if patients receive early treatment with corticosteroids.

Researchers at the University of Hong Kong analysed cases of Bell's palsy related to the two approved vaccines in Hong Kong -- China's CoronaVac and US-based Pfizer.

The team found that for every 100,000 people vaccinated with China's inactivated vaccine CoronaVac, an additional 4.8 people may develop the condition, but for the Pfizer-BioNTech vaccine, the increased risk was equivalent to an additional 2 cases per 100,000 people vaccinated.

For the study, the team included 298 Bell's palsy cases and 1,181 matched controls from 2010-2020.

The team estimated the background risk of Bell's palsy in Hong Kong -- around 27 cases per 100,000 people, per year. Global estimates range from 15-30 cases per 100,000 people, per year.

The study found that receiving CoronaVac was associated with 2.4 times increased risk of Bell's palsy (95 per cent) whereas receiving Pfizer vaccine was not associated with a significantly increased risk.

"Our study suggests a small increased risk of Bell's palsy associated with CoronaVac vaccination. 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," said lead author Professor Ian Chi Kei Wong, from the varsity.

"Ongoing surveillance, through pharmacovigilance studies such as ours are important to calculate with increasing levels of confidence the risks of rare adverse events," Wong added.

However, the team noted that the study is limited to patients with a new diagnosis of Bell's palsy in Hong Kong, so further studies in other regions should be done to confirm the findings.

The US Federal Drug Administration (FDA) does not consider a clear causal association between the condition and vaccines by Pfizer-BioNTech and the Moderna, but recommends ongoing surveillance. Acute partial facial paralysis is reported as a rare side effect of both vaccines by the European Medicines Agency.