%5B3%5D.jpg)
For those who are interested in ancient public health history, I gave my account of those events 15 years ago, in Deja Flu, All Over Again.
Since then, flu vaccine technology has improved markedly, and subsequent studies have shown only a very small risk of developing GBS following receipt of a flu vaccine (see the CDC's Guillain-Barré Syndrome (GBS) and Vaccines).
Even without vaccines, there is always a background rate of GBS - usually 1 to 2 cases per 100,000 each year - often linked to viral or bacterial infections. The CDC describes the disorder:While there is a small risk of developing GBS from a vaccine, most studies show you are far more likely to develop the condition after a viral or bacterial infection, than you are after getting a vaccine.
What is Guillain-Barré syndrome (GBS)?
Guillain-Barré syndrome (GBS) is a rare disorder in which a person’s own immune system damages their nerve cells, causing muscle weakness and sometimes paralysis. GBS can cause symptoms that usually last for a few weeks. Most people recover fully from GBS, but some people have long-term nerve damage. In very rare cases, people have died of GBS, usually from difficulty breathing. In the United States, an estimated 3,000 to 6,000 people develop GBS each year.
What causes GBS?
The exact cause of GBS is unknown, but about two-thirds of people who develop GBS experience symptoms several days or weeks after they have been sick with diarrhea or a respiratory illness. Infection with the bacterium Campylobacter jejuni is one of the most common risk factors for GBS. People also can develop GBS after having the flu or other infections (such as cytomegalovirus and Epstein Barr virus). On very rare occasions, they may develop GBS in the days or weeks after getting a vaccination.Clusters of GBS are relatively rare, but we have looked at a few (see 2011's The Sonora/Arizona GBS Cluster). In this particular case, the outbreak was linked to inadequately disinfected tap water (see Binational outbreak of Guillain-Barré syndrome associated with Campylobacter jejuni infection, Mexico and USA, 2011).
Following the 2015/2016 outbreak and spread of the Zika virus in the Americas, Zika virus infection has been linked to the development of GBS . We've also seen repeated outbreaks reported over the past 5 years in Peru.
While no vaccine can claim to be 100% safe or benign, the (non-mRNA) Janssen (J&J) COVID-19 vaccine was associated with a slightly increased risk of side effects (see FDA Limits The Authorized Use Of The Janssen COVID Vaccine) - including GBS.
In 2023, in Neurology: Association Between Guillain-Barré Syndrome and COVID-19 Infection and Vaccination, we saw a study that found the risks of developing GBS increased 6-fold following COVID infection, while receipt of the COVID vaccine was linked to a significantly decreased risk.
Still, the anti-vaccine rhetoric on the internet continues full-throttle, demonizing mRNA vaccines in particular.
While I don't expect it to convince those who deeply distrust science, we have a new study today indicating that while the risks of developing GBS following receipt of an adenovirus-vectored vaccine - or COVID Infection - were elevated, those risks decreased after receipt of an mRNA COVID vaccine .
First a link, and some excerpts, from the study. Followed by a press release from the University of Auckland.Risk of Guillain-Barré syndrome after COVID-19 vaccination or SARS-CoV-2 infection: A multinational self-controlled case series study
Sharifa Nasreen a b, Yannan Jiang c d, Han Lu c d, Arier Lee c d, Clare L. Cutland e, Angela Gentile f, Norberto Giglio f, Kristine Macartney g, Lucy Deng g, Bette Liu g, Nicole Sonneveld g, Karen Bellamy h, Hazel J. Clothier d i, Gonzalo Sepulveda Kattan d i, Monika Naus j, Zaeema Naveed j k, Naveed Z. Janjua j k, Lena Nguyen a, Anders Hviid l, Eero Poukka m n…Jeffrey C. Kwong a adShow more
https://doi.org/10.1016/j.vaccine.2025.127291Get rights and content
Under a Creative Commons license
Abstract
Background
The association between Guillain-Barré syndrome (GBS) and certain COVID-19 vaccines is inconclusive. We investigated the risk of GBS after COVID-19 vaccination or SARS-CoV-2 infection.
Methods
Using a common protocol, we conducted a self-controlled case series study from 1 December 2020 to 9 August 2023 at 20 global sites within the Global Vaccine Data Network™ (GVDN®). Brighton Collaboration case definition criteria were used to determine the level of certainty (LOC) of medical record-reviewed GBS cases at 15 sites. GBS cases following SARS-CoV-2 infection were identified from electronic data sources (EDS) from 11 sites. We estimated the relative incidence (RI) of GBS within 1–42 days following receipt of adenoviral vector, mRNA, or inactivated COVID-19 vaccines or SARS-CoV-2 infection using conditional Poisson regression models, controlling for seasonality. We used random effects meta-analysis to pool the estimates across sites.
Results
Of 410 medical record-reviewed post-vaccination GBS cases (out of 2086 EDS-identified cases), 49 were LOC 1 or 2, 187 were LOC 3 or 4, and 174 were LOC 5. These cases received a total of 794 doses of COVID-19 vaccines (160 [20 %] adenoviral vector vaccine doses, 556 [70 %] mRNA vaccine doses, 77 [10 %] inactivated vaccine doses, and 1 [0.1 %] protein-based vaccine dose) during the observation period.
We observed an increased risk of confirmed (LOC 1–2) GBS after receiving ChAdOx1-S/nCoV-19 (Vaxzevria/Covishield) (RI = 3.10; 95 % confidence interval [CI], 1.12–8.62).
Decreased risks of LOC 1–4 GBS were observed after receiving BNT162b2 (Comirnaty/Tozinameran) (RI = 0.48; 95 %CI, 0.27–0.85) and CoronaVac/Sinovac (RI = 0.04; 95 %CI, 0.00–0.61). For 489 EDS-identified GBS cases after SARS-CoV-2 infection, we found GBS risk to be increased (RI = 3.35; 95 %CI, 1.83–6.11).
Conclusion
In this large multinational study, we found increased risks of GBS within 42 days after Vaxzevria/Covishield vaccination or SARS-CoV-2 infection, and decreased risks after receiving Comirnaty/Tozinameran or CoronaVac/Sinovac COVID-19 vaccines.
4. Discussion
In this large, multinational study covering more than 230 million people observed from 1 December 2019 to 9 August 2023, we found that receipt of adenoviral vector vaccines, particularly Vaxzevria/Covishield, and SARS-CoV-2 infection were both associated with an approximately three-fold increased risk of confirmed GBS during the 1–42 days post exposure, whereas receipt of mRNA vaccines (specifically Comirnaty/Tozinameran) was associated with an approximately 30–50 % decreased risk of GBS.
(SNIP)
5. Conclusion
In this large multinational study, we found comparably increased risks of GBS after Vaxzevria/Covishield vaccination or SARS-CoV-2 infection, and decreased risks after receiving Comirnaty/Tozinameran or CoronaVac/Sinovac, suggesting that mRNA or inactivated vaccines may be preferable to adenoviral vector vaccines to minimize the risk of GBS. Since new vaccines continue to be developed using the non-replicating viral vector platform, continued safety monitoring and evaluation of both existing and emerging vaccine platforms are essential to inform vaccine policy decisions.
From the University of Auckland, some excerpts from a press release on this study:
Covid and certain vaccines linked to syndrome risk
4 June 2025
A global study, covering more than 230 million people, sheds light on the relationship between Guillain-Barré syndrome after certain Covid vaccines or SARS-CoV-2 infection.
People infected with SARS-CoV-2 were around three times more likely to develop Guillain-Barré syndrome within six weeks of infection compared with other times, suggesting that infection with this virus increases the risk of Guillain-Barré syndrome.
An increased risk was also observed following adenoviral vector vaccines (AstraZeneca, Janssen/Johnson & Johnson), but not after mRNA vaccines (Pfizer-BioNTech, Moderna) or inactivated vaccines (Coronavac/Sinovac).
“If you are concerned about the risk of rare but serious side effects of vaccines such as Guillain-Barré syndrome, you should know that receiving an mRNA COVID-19 vaccine does not appear to increase your risk, but infection with the virus does,” said Dr Jeff Kwong, senior author for the study based at ICES and the University of Toronto in Canada.
“This study reinforces what we have known for some time – the potential health risks from Covid-19 disease are greater than the risks following Covid-19 vaccination, which plays an important role in protecting us from serious risks posed by infection.
Although most vaccines - including the COVID mRNA vaccines - have an enviable safety record, there is no such thing as a 100% safe drug or medication for 100% of the population.
The decision to take any vaccine or medication always involves a risk-reward calculation. Most of the time, the small risk from a vaccine is justified, given the protection it provides.Even over-the-counter remedies, like NSAIDs or acetaminophen, can sometimes produce adverse - even fatal - reactions (see BMJ Research: NSAIDs & The Risk Of Heart Failure).
For those who are still planning on getting the COVID shot/booster this fall (as am I), todays' study should provide some additional reassurance.
