Getting coronavirus is associated with a greater risk of rare neurological complications than a first vaccine dose, a new study suggests.
According to the research, people who received the Oxford/AstraZeneca jab had an increased risk of developing two types of complications – Bell’s palsy and Guillain-Barre syndrome – in the 28 days after receiving their first dose.
Those receiving the Pfizer vaccine had an increased risk of haemorrhagic stroke.
Bell’s palsy is a short-term weakness in one side of the face, while Guillain-Barre syndrome is a very rare condition that affects the nerves, resulting in numbness and weakness, and haemorrhagic stroke is caused by bleeding in the brain.
However, Covid-19 infection carried a much higher risk of developing neurological complications than either vaccine, the research suggested.
Scientists assessed the risk of developing neurological complications within 28 days of a first dose of either the Oxford or Pfizer vaccines, or within 28 days of a positive PCR test.
They found that both vaccines resulted in an increase of certain types of neurological adverse events for a short time after administration, but that infection with Covid-19 led to a greater risk than receiving either vaccine.
Martina Patone, medical statistician at the Nuffield Department of Primary Care Health Sciences, University of Oxford, and co-lead author, said: “We found different risks for different types of neurological condition depending on which vaccine people received.
“However, these were substantially lower than the risks occurring in association with a positive Covid-19 PCR test.
“For example, we estimate 145 excess cases of Guillain-Barre syndrome per 10 million people in the 28 days after a positive SARS-CoV-2 test, compared to 38 per 10 million for those who received the ChAdOx1nCoV-19 vaccine.”
Dr Lahiru Handunnetthi, clinical lecturer at the Nuffield Department of Clinical Neurosciences, University of Oxford, and co-lead author of the paper, said: “In our study of over 32 million people, we found that several neurological complications such as Guillain-Barre syndrome were linked to both Covid-19 infection and first-dose vaccination.
“These neurological complications were very rare, but awareness of these will be important for patient care during mass vaccination programmes across the world.”
Researchers also carried out an additional analysis limited to people who tested before vaccination.
This did not change their results, indicating a greater risk of all neurological complications following infection before vaccination.
However, the number of people infected after vaccination was too small for a separate analysis, according to the study, published in Nature Medicine.
Julia Hippisley-Cox, professor of clinical epidemiology and general practice at the University of Oxford, and co-author, said: “We know the Covid-19 vaccines are very effective at reducing risks of severe outcomes from Covid-19 infection.
“Whilst there are some increased risks of very rare neurological complications associated with the Oxford/AstraZeneca vaccine, these are much smaller than the risks associated with Covid infection itself.
“However, these very rare conditions are very important to spot to ensure that clinicians know what to look for, aid earlier diagnosis, and inform clinical decision-making and resource management.”
The findings are based on the analysis of anonymised healthcare records of more than 32 million people across England.