A nationwide analysis of 32 million adults in England revealed an increased, but low, risk of the rare neurological conditions Guillain–Barré syndrome and Bell’s palsy following a first dose of the Oxford–AstraZeneca (ChAdOx1nCoV-19) vaccine. There was also an increased, but low, risk of hemorrhagic stroke following a first dose of the Pfizer–BioNTech (BNT162b2) vaccine. However, the research, published in Nature Medicine, also found that there was a substantially higher risk of seven neurological outcomes studied, including Guillain–Barré syndrome, after a positive SARS-CoV-2 test. The authors emphasize that the observed neurological complications associated with the Oxford–AstraZeneca and Pfizer–BioNTech vaccines are rare, and the risk of neurological disorders as a result of SARS-CoV-2 infection is much greater.
Several vaccines, including the Oxford–AstraZeneca and Pfizer–BioNTech vaccines, are approved for use in multiple countries and have been shown to reduce SARS-CoV-2 infections, transmissions, hospitalizations and deaths. However, there have been reports of rare neurological complications associated with SARS-CoV-2 infection and vaccines.
To investigate the possibility of an association between vaccinations and SARS-CoV-2 infection and the development of neurological disorders, Julia Hippisley-Cox and colleagues conducted a self-controlled case study series that examined hospital admissions for neurological complications in the 28 days following a first dose of the Oxford–AstraZeneca or Pfizer–BioNTech vaccine, or a positive test for SARS-CoV-2. The authors found that there was an increased risk of Guillain–Barré syndrome in the 28 days following vaccination with the Oxford–AstraZeneca vaccine — an estimated 38 excess cases per 10 million people vaccinated. An increased risk of Bell’s palsy was also noted 15–21 days following vaccination; however, this risk was not significant over the whole 28-day study period. There was also an increased risk of hemorrhagic stroke within 28 days following vaccination with the Pfizer-BioNTech vaccine — namely, an estimated 60 extra cases per 10 million people. Within this same time period following a positive SARS-CoV-2 test, there was a substantially higher risk of all seven neurological outcomes studied, including encephalitis meningitis and myelitis, myasthenic disorders, and Guillain–Barré syndrome — amounting to 123, 163, and 145 excess cases per 10 million people, respectively. The authors replicated their findings in an independent national cohort of more than three million people from Scotland, which provided support for the association between the Oxford–AstraZeneca vaccine and Guillain–Barré syndrome.
The authors anticipate that these results will inform risk–benefit evaluations for vaccine programs as well as clinical decision making and resource allocation for these rare neurological complications. They conclude that these findings are likely to be of relevance to other countries; however, it would be useful to replicate the findings in similarly large datasets, internationally.
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