A study of over 8 million participants found no correlation between COVID-19 vaccination and developing neurological conditions. However, a risk of some neurological conditions was increased after COVID-19 infection.
The approved vaccines are highly effective against preventing severe COVID-19 disease, hospitalization, and death. However, the rapid rollout of the vaccines left some unanswered questions about the long-term effects of COVID-19 vaccination.
One study, published today in The BMJ, examined the association between COVID-19 vaccines, COVID-19 infection, and risk of immune meditated neurological events. The investigators looked for evidence of 4 neurological conditions: Bell’s palsy (facial weakness), encephalomyelitis (inflammation of the brain and spinal cord), Guillain-Barré syndrome (a nerve condition), and transverse myelitis (inflammation of the spinal cord).
The study included 8330497 people who received at least 1 dose of a COVID-19 vaccine by January 13, 2022, ascertained from primary care records in the UK and Spain. At the time, there were 5 COVID-19 vaccines authorized by the European Medicines Agency, including the Pfizer-BioNTech and Moderna mRNA vaccines, the Oxford-AstraZeneca and Janssen viral vector vaccines, and the recombinant spike protein nanoparticle vaccine Novavax.
Overall, 4376535 people received AstraZeneca, 3588318 received Pfizer-BioNTech, 244913 received Moderna, and 120731 received Janssen. The study also included a total of 735870 unvaccinated people infected with COVID-19, and 14330080 people from the general population, studied retroactively to estimate historical background pre-pandemic.
The patient primary care records came from The Clinical Practice Research Datalink (CPRD) AURUM in the UK, and the Information System for Research in Primary Care (SIDIAP) database in Spain.
Post-vaccination rates of Bell’s palsy, encephalomyelitis and Guillain-Barré syndrome were consistent with rates established from the background study cohort. Transverse myelitis events were < 5 in all vaccinated groups and could not be analyzed.
Notably, rates of Bell’s palsy, encephalomyelitis and Guillain-Barré syndrome were all higher than anticipated after COVID-19 infection. The study was not causational, so the investigators did not speculate on why this was. Broken down by individual risk the increased likelihood of developing a neurological condition after COVID-19 infection was small, but even a small risk can burden the healthcare system.
The results from such large studies show that neurological conditions are no more common among vaccinated people than among unvaccinated people (without prior COVID-19 infection). “We may never be able to tell exactly what caused an individual to develop a neurological condition, but COVID-19 vaccination is a highly unlikely reason for most,” the investigators concluded.