There is no increased risk of rare neurological events following COVID-19 vaccination, according to new evidence published today.
The study of more than eight million people found there is an increased risk of Bell’s palsy, encephalomyelitis and Guillain-Barré syndrome after COVID-19 infection.
The study, published in today’s edition of The BMJ, was undertaken after reports of some people developing Guillain-Barré syndrome after receiving the Oxford-AstraZeneca or Pfizer-BioNTech COVID-19 vaccines.
While the European Medicines Agency listed Guillain-Barré syndrome as a rare side effect of these vaccines, research into the risk of Guillain-Barré syndrome and other immune mediated neurological disorders after COVID-19 vaccination have been mixed.
In this study, researchers analysed data from two large electronic primary care health record databases in the UK and Spain, which included 8.3 million individuals who received at least one dose of the Oxford-AstraZeneca, Pfizer-BioNTech, Moderna or Johnson & Johnson COVID-19 vaccine and 735,870 unvaccinated individuals with a positive COVID-19 test result.
They also studied retrospectively – before the pandemic – 14.3 million people from the general population retrospectively to estimate historical background rates.
The team, from the University of Oxford, UK, and Barcelona, Spain, looked for evidence of four immune mediated neurological disorders: Bell’s palsy, encephalomyelitis, Guillain-Barré syndrome, and transverse myelitis.
They estimated rates of these disorders in the 21 days after the first vaccine dose, 90 days after a positive COVID-19 test result, and between 2017 and 2019 for background rates in the general population group.
Post-vaccine rates were consistent with expected population rates for Bell’s palsy, encephalomyelitis and Guillain-Barré syndrome, while transverse myelitis was found to be fewer than 5 events in all vaccinated groups, so could not be analysed.
After COVID-19 infection, rates of Bell’s palsy, encephalomyelitis and Guillain-Barré were higher than expected.
Although this was an observational study, the researchers say they cannot rule out the possibility that unknown differences between groups or misclassification of disorders may have affected their results.
But they add that several studies have also reported increased risks of immune mediated neurological events after COVID-19 infection, which suggests their results are robust.
“We found no safety signal for any of the studied immune mediated neurological events after vaccination against COVID-19. Infection with SARS-CoV-2 was, however, associated with an increased risk of Bell’s palsy, encephalomyelitis, and Guillain-Barré syndrome,” they conclude.
They add that further evidence is needed to understand the long term adverse events of vaccination and SARS-CoV-2 infection, while larger cohorts are also needed to study the effect of vaccination on different age groups.
Li X, Raventós B, Roel E et al. Association between COVID-19 vaccination, SARS-CoV-2 infection, and risk of immune mediated neurological events: population based cohort and self-controlled case series analysis. BMJ 17 March 2022; doi.org/10.1136/ bmj-2021-068373
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