The coronavirus is associated with a greater risk of developing a rare stroke than a dose of the vaccine, according to a new study.
The study published in Nature Medicine draw upon data from 32 million patient records from England.
Patients having the Pfizer/BioNTech vaccine had an increased risk of haemorrhagic stroke in the 28 days after their first jab at a rate of 60 extra cases per 10 million people vaccinated.
However, Covid infection carried a much greater risk of developing complications than either the Pfizer/BioNTech vaccine or the Oxford AstraZeneca jab, which was linked to rare cases of Bell’s palsy and Guillain-Barre syndrome.
Study co-author Dr Lahiru Handunnetthi, clinical lecturer at the Nuffield Department of Clinical Neurosciences, University of Oxford, 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.”
Several experts urged caution in drawing conclusions from the association between the Pfizer/BioNTech vaccine and haemorrhagic stroke.
Prof Penny Ward, Professor in Pharmaceutical Medicine at King’s College London, noted that the link revealed in data from England was not confirmed by data from Scotland and was still outranked by the greater risk associated with Covid infection.
Prof David Werring, Professor of Clinical Neurology, UCL Institute of Neurology, UCL, said: “The finding was not replicated using Scottish cohort data since there were too few events to obtain reliable estimates.
“So, although a low platelet count (which could be a risk for intracerebral haemorrhage) has previously been reported after the Pfizer-BioNTech vaccine, any possible association with intracerebral haemorrhage needs further independent confirmation in similarly large datasets internationally, ideally with validation of the diagnostic coding.”
Haemorrhagic strokes occur when a blood vessel inside the skull bursts and bleeds into the brain.
These are much less common than ischemic strokes, accounting for around 15% of strokes in the UK.
