Is there a link between COVID-19 or the COVID-19 vaccination and certain neurological disorders?

A European Health Data Evidence Network study analysed records from over 8 million people from the UK and Spain.

The study found no evidence of a link between the COVID-19 vaccines and three neurological disorders studied.

However, people who had the illness caused by COVID-19 were at an increased risk of three of those four neurological disorders

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Why was this work needed?

Huge national and international COVID-19 vaccination programmes started as early as December 2020 with nearly 10 billion doses given (up to January 2022). Public concern had been raised about the rapid development of COVID-19 vaccines given that previously medical trials may take many years before a drug/device is licensed for use in humans. This has led to questioning if side effects are increased and in particular if these vaccines may affect the nervous system.

Previous research into any increased risk of neurological disorders following COVID-19 vaccination had produced differing results.

In 2021 the European Medicines Agency (EMA) added Guillain-Barré syndrome to the list of very rare side effects of COVID-19 vaccines produced by Oxford Astra-Zeneca, Pfizer BioNTec and Janssen. Guillain-Barré syndrome is a serious condition that affects the nerves in the feet, hands and limbs, causing problems such as numbness, weakness, pain and problems with balance and co-ordination. It can occasionally be life-threatening and leave those affected with long-term problems. This action by the EMA was due to 941 reported cases of people developing this syndrome after receiving the Oxford Astra-Zeneca or Pfizer BioNTec vaccines.

What was the aim of the research?

The aim of the research was to identify any relationships between COVID-19 vaccines, infection with SARS CoC 2 (the virus that causes COVID-19) and 4 nervous system disorders:

  • Guillain-Barré syndrome
  • Bell’s palsy (facial weakness)
  • Encephalomyelitis (inflammation of the brain and spinal cord)
  • Transverse myelitis (inflammation of the spinal cord)

Comparisons were made between the number for each of the above disorders diagnosed at 3 different time points allowing researchers to compare usual pre-pandemic rates of these disorders with those who contracted COVID-19 and who were either vaccinated or not vaccinated

  • In the period from 2017 to 2019 (i.e., prior to the COVID-19 pandemic)
  • Up to 90 days after a positive test result for SARS-CoV-2
  • Up to 21 days after a first vaccine dose (estimated numbers)

What did research find?

The research did not find any clear connection between COVID-19 vaccines and Guillain-Barré, Bell’s palsy and encephalomyelitis.

Transverse myelitis was rare, less than 5 people were affected who had been vaccinated and the data could not be analysed.

However, there was an increased risk of Guillain-Barré syndrome, Bell’s palsy, and encephalomyelitis, seen in people who had the SARS-CoV-2 (COVID-19) infection.

What is the impact on patients?

Although neurological conditions do occasionally occur shortly after COVID-19 vaccination, good evidence from very large studies shows that these conditions are no more common among vaccinated people than among unvaccinated people. In other words, having the vaccination does not appear from this research to increase that risk.

What data was used?

Anonymised data from the primary care records of over 8 million people from both the UK and Spain was used. In the UK the Clinical Practice Research Datalink (CPRD) was the data source. This Datalink is an ongoing primary care database of anonymised medical records from general practitioners, representing 20% of the current UK population. Data from Spain came from the Information System for Research in Primary Care ( SIDIAP), a primary care database that covers 80% of the population in Catalonia, Spain, and is linked at an individual level to hospital data.

Who funded and collaborated on this work?

The research was funded by the UK National Institute for Health Research (NIHR) and the European Health Data and Evidence Network (EHDEN), a European project with many academic, healthcare, pharmaceutical industry collaborators and a European patients’ organisation, that uses secure networks of health data all over Europe to conduct large-scale health data research. This research was conducted by researchers at the University of Oxford (UK), and researchers from institutions in Barcelona (Spain) and Rotterdam (Netherlands).

This work uses data provided by patients and collected by the health professionals as part of the care and support provided.