Guillain-Barré Syndrome in COVID-19 Vaccine Trial Does Not Imply Causality, Experts Say


Authors of a paper published in Neurology suggest that a case of Guillain-Barré Syndrome reported in a COVID-19 vaccine trial may have been a coincidence.


In a COVID-19 vaccine trial, an individual who received the vaccine subsequently developed Guillain-Barré syndrome (GBS); however, authors of a recently published paper are cautioning that this does not prove that the vaccine was the cause.1

The findings come from a case report published in Neurology, which detailed that 2 individuals participating in a COVID-19 vaccine trial developed GBS, a rare autoimmune disorder. One of the participants had received the COVID-19 vaccine, whereas the other participant had received a placebo of saline.1

Although rare, GBS can occur after gastrointestinal or respiratory infections and can be life-threatening. However, most individuals recover with few complications. The exact cause of the disorder is unknown and whether vaccinations can increase the risk of GBS is uncertain.2

More and more Americans are willing to receive the COVID-19 vaccine. However, reports of potentially concerning adverse effects (AEs), although rare, may raise fears about the safety of these vaccines, particularly among those who are already hesitant.

“COVID-19 vaccines currently being administered in the United States have been shown to be safe and effective at reducing risk of severe illness and death and are saving lives,” said case report author Anthony A. Amato, MD, of Harvard Medical School in Boston, Massachusetts and a Fellow at the American Academy of Neurology.2 “With approximately 1 billion people worldwide expected to be vaccinated against COVID-19, we anticipate there could be thousands of cases of Guillain-Barré syndrome that will occur around the time of the vaccination only by coincidence.”

According to documents submitted to the FDA for emergency use authorization of the Johnson & Johnson COVID-19 vaccine, 2 individuals in the clinical trial (1 in the placebo group and 1 in the active arm) developed GBS within 2 weeks of receiving an injection.1

According to the case report published in Neurology, a 60-year-old woman who did not have COVID-19 antibodies, respiratory and gastrointestinal illness at the start of the trial, received the Johnson & Johnson vaccine in December 2020. Ten days following vaccination, the woman developed symptoms of GBS and was treated with intravenous immunoglobulin. She was discharged to rehabilitation after 10 days of hospital admission.1

However, the case report authors noted the incidence of GBS was identical in both arms of the trial; the patient in the vaccine arm did not have any clinical features differentiating her from patients with typical GBS.1

“From the available evidence, it is not possible to draw causal inferences about the association of COVID-19 vaccination and the development of GBS,” the authors wrote.1 They emphasized that, by chance alone, it is estimated that 900 to 2000 individuals will develop GBS within 6 weeks of receiving a 1-dose vaccine. As such, they cautioned against misattributing AEs to the vaccination program.

“We also advise our patients with prior GBS that there is no contraindication to receiving any COVID-19 vaccination and they should get vaccinated as soon as possible,” the authors concluded.1

Pharmacists should also be prepared to address concerns expressed by patients when reports of GBS and COVID-19 vaccines appears in the news.

In an accompanying editorial, the authors advised providers to3:

  • Educate that such associations are most likely coincidental and it is unlikely that COVID-19 vaccinations cause GBS.
  • Provide reassurance that there is ongoing monitoring of serious health problems following vaccinations.
  • Emphasize that preventing COVID-19 outweighs any theoretical risks of GBS following vaccinations.


  1. Márquez Loza AM, Holroyd KB, Johnson SA, Pilgrim DM, Amato AA. Guillain-Barré syndrome in the placebo and active arms of a COVID-19 vaccine clinical trial: Temporal associations do not imply causality. Neurology. Published online April 6, 2021. doi: 10.1212/WNL.0000000000011881
  2. COVID-19 Trial: One Case of Guillain-Barré After Vaccine, But Also One After Placebo. News release. American Academy of Neurology; April 6, 2021. Accessed April 12, 2021.
  3. Bourdette D, Killestein J. Quelling public fears about Guillain-Barré syndrome and COVID-19 vaccination. Neurology. Published online April 6, 2021. Doi: 10.1212/WNL.0000000000011882
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