A study of 32 million UK adults suggests that the AstraZeneca COVID-19 vaccine is in rare cases associated with Guillain-Barré syndrome and the Pfizer vaccine with stroke – but that neurological complications are far more common following infection with SARS-CoV-2.
The research, published in Nature Medicine, is the first to robustly investigate the link between COVID-19 vaccines and rare neurological complications.
With the pandemic showing little sign of abating, and extremely high rates of infection in many countries, [the study] emphasises the importance of accepting the offer of a COVID-19 vaccine if doses are available.
What did the researchers do?
Martina Patone and colleagues at the University of Oxford, UK, analysed healthcare records from more than 32 million people across England, assessing the risk of hospital admission or death for seven different neurological complications within 28 days of receiving a first dose of either the Oxford/AstraZeneca or Pfizer/BioNTech vaccines, or within 28 days of a positive COVID-19 PCR test.
They only looked at the risks associated with the first vaccine dose, as data on outcomes following second doses was limited at the time of the study. They also didn’t look at milder neurological disease associated with vaccination or infection.
What did they find?
They found that both vaccines resulted in a very slight increased risk of certain types of neurological complications. For the Oxford/AstraZeneca vaccine, there was a very small increased risk of Guillain-Barré syndrome – a rare disorder in which the body’s immune system mistakenly attacks the nerves, triggering numbness, weakness and pain. The increase was equivalent to an extra 38 cases per 10 million people vaccinated – roughly one in 260,158.
For the Pfizer/BioNTech vaccine, there was a very slight increased risk of haemorrhagic stroke – where a blood vessel in the brain ruptures, causing blood to leak into the brain tissue – within 28 days of being vaccinated. Here, the increase was equivalent to 60 extra cases per 10 million people vaccinated – roughly 1 in 166,667. Women were more frequently affected, for unknown reasons.
However, for those people testing positive for COVID-19, there was a substantially higher risk of developing seven different neurological complications in the following 28 days. This included inflammation of the brain, the tissue surrounding the brain (encephalitis meningitis), or the spinal cord (myelitis) – which can result in symptoms such as paralysis, sensory loss or seizures; myasthenic disorders, caused by a defect in the transmission of signals from nerve cells to muscles; Bell’s palsy, a temporary weakness or lack of movement affecting one side of the face; as well as brain bleeds and Guillain-Barré syndrome.
For encephalitis meningitis and myelitis, the increased risk was equivalent to 123 extra cases per 10 million people; for myasthenic disorders it was equivalent to 163 extra cases per 10 million people, while for Guillain-Barré syndrome, it was equivalent to 145 extra cases per 10 million people.
The authors replicated their findings in an independent national cohort of more than three million people from Scotland. This provided support for the association between the Oxford/AstraZeneca vaccine and Guillain-Barré syndrome, but not the association between the Pfizer/BioNTech vaccine and stroke. Further validation of this finding is therefore warranted, they said.
What are the implications of this research?
This study confirms previous reports that the Oxford/AstraZeneca vaccine is associated with an increased risk of Guillain-Barré syndrome, but that this is extremely rare. It also highlights the possibility that the Pfizer/BioNTech vaccine is associated with an increased risk of haemorrhagic stroke, although this too is extremely rare and requires further confirmation.
However, the risks of neurological complications with either vaccine are much smaller than the risks of neurological complications associated with COVID-19 infection itself. With the pandemic showing little sign of abating, and extremely high rates of infection in many countries, it emphasises the importance of accepting the offer of a COVID-19 vaccine if doses are available.
Awareness of these very rare conditions and their association with COVID-19 and/or certain COVID-19 vaccines is also important, to ensure that doctors know what to look for and rapidly provide the appropriate treatment when they do occur.