Researchers from the University of Oxford analysed the healthcare records of more than 32 million people in England and found that Guillain-Barre syndrome, Bell’s palsy and haemorrhage stroke were linked to both infection and vaccination.
However, while a first dose of the AstraZeneca and Pfizer vaccine can lead to the development of an adverse neurological event shortly after administration, infection from Covid-19 carries a far greater risk than either jab.
The study, published in Nature Medicine, estimates that there were 38 excess cases of Guillain–Barre syndrome per 10 million people given the AstraZeneca vaccine, compared to 145 cases per 10 million after testing positive for Covid-19.
Dr Lahiru Handunnetthi, a co-author of the study, 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.”
Initial vaccine clinical trials were not large enough to be able to detect very rare adverse neurological events – those that happen in less than one person out of 10,000.
The Oxford study was able to achieve this by looking at the real-world data from millions of healthcare records in England.
The authors also report an association between the Pfizer vaccine and haemorrhagic stroke, though experts not involved in the study have questioned this link due to the weakness of the data.
“This was only seen in one cohort, it wasn’t also found in the Scottish data, and it looks to me a very small signal and possibly not very significant,” said Peter Openshaw, a professor of experimental medicine at Imperial College London.
He said other adverse events linked to both the Pfizer and AstraZeneca vaccines “were dwarfed by the neurological disorders seen after testing positive for Covid: Guillain–Barre syndrome, myasthenia-like disease, subarachnoid haemorrhage, encephalitis, and Bell’s palsy were all quite common, especially in the first two weeks after testing positive for Sars-CoV-2.
“The neurological complications of Sars-CoV-2 vaccines are much rarer than the neurological complications of Covid-19, showing the vital importance of getting vaccinated.”
Aziz Sheikh, professor of primary care research and development at the University of Edinburgh and a co-author of the paper, said: “A key strength of this study was that we were able to replicate the analysis in Scotland’s national Covid-19 dataset.
“Overall, this provided strong support to the findings observed in the English dataset.”
The authors of the study acknowledged a number of limitations to their findings; only risks associated with the first vaccine dose were examined, as data on outcomes following second doses was limited at the time of the research.
And only hospital admissions and mortality were included in the examined healthcare data, so patients with milder neurological disease may not have been included and the overall burden of neurological adverse events from vaccination and infection could be underestimated.
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