Some people developed Guillain-Barr syndrome after receiving the Oxford-AstraZeneca or Pfizer-BioNTech covid vaccines, as the European Medicines Agency listed Guillain-Barr syndrome as a rare side effect of these vaccines.
However, so far the research results on the risk of Guillain-Barr syndrome and other immune-mediated neurological disorders after the COVID-19 vaccination have been mixed.
To address this, researchers began studying the link between the COVID-19 vaccine, SARS-CoV-2 (the virus that causes COVID-19), and the risk of immune mediated neurological events. Their findings were based on the data from two large electronic primary care health record databases in the UK and Spain.
Of those, 8.3 million received at least one dose of one COVID-19 vaccine (Oxford-AstraZeneca, Pfizer-BioNTech, Moderna, or Johnson & Johnson) and 735,870 non-vaccinated individuals had a positive COVID-19 test result.
A further 14.3 million people from the general population were also retrospectively studied (before the pandemic) to assess historical background rates. This group was not vaccinated and did not have a previous covid because neither was present at the time.
The special events to the research team were four immune mediated neurological disorders: Bell’s palsy, encephalomyelitis, Guillain-Barr syndrome, and transverse myelitis (inflammation of the spinal cord).
Rates of these disorders were estimated between 21 days after the first vaccine dose and 90 days after the positive test result, with background rates in the general population between 2017 and 2019.
Overall, the researchers found that post-vaccination rates were consistent with expected (background) population rates for Bell’s palsy, encephalomyelitis, and Guillain-Barr syndrome. Rates of transgenic myelitis were rare (less than 5 cases in all vaccinated groups) so could not be analyzed.
However, the rates of these items were higher than the expected after COVID-19 infections. This is an observational study, so the cause cannot be established, and researchers cannot rule out the possibility that unknown differences between groups or incorrect classification of disorders may have influenced their results.
But several studies point to an increase in the risk of immune mediated neurological events after COVID-19 infection, and their results are strong.
As such, they say, “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-Barr syndrome.”
Further evidence is needed to understand the long-term adverse events of COVID infection and vaccination, while larger cohorts are also needed to study the effect of vaccination on different age groups, mainly among young people, they add.
Importantly, all the risks even those observed after COVID-19 infection are completely small for an individual, experts write in the linked editorial. However, they also note that even small absolute risks “can lead to a substantial burden on the healthcare system in the context of mass vaccination and widespread infection.”
Researchers and clinicians are responsible for discussing these findings with affected patients and their families, while acknowledging the inherent uncertainty in making patient-level assumptions from demographic studies.
One approach that illustrates the good evidence from the larger studies is that although neurological conditions rarely occur shortly after the COVID-19 vaccine is given, these conditions are not as prevalent among those who have been vaccinated as those who have not been vaccinated.
“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,” they conclude.
Source: Medindia
