CDC study shows risk of Guillain-Barré syndrome elevated after Ad.26.COV2.S COVID vaccination

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Thanks to the relentless efforts of medical researchers around the world, several different messenger ribonucleic acid (mRNA) and vector-based vaccines were authorized for use by regulatory bodies worldwide.

Study: Guillain-Barré Syndrome after COVID-19 Vaccination in the Vaccine Safety Datalink. Image Credit: PalSand /

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources


To date, three vaccines have been authorized for emergency use or FDA-approved in the United States (U.S.) to prevent coronavirus disease 2019 (COVID-19). These vaccines include BNT162b2 (Pfizer-BioNTech - FDA-approved) and mRNA-1273 (Moderna -authorized for emergency use), both of which are mRNA-based vaccines, as well as Ad.26.COV2.S (Janssen -authorized for emergency use).

BNT162b2 and mRNA-1273 are both administered primarily as double-doses, with a third booster shot that has recently been approved after six months. The Ad.26.COV2.S is a replication-incompetent adenoviral vector vaccine and is primarily administered as a single dose; however, the U.S. Food and Drug Administration (FDA) has recently advised Ad.26.COV2.S recipients to receive a booster dose of any approved COVID-19 vaccine after two months.

Guillain-Barré syndrome (GBS) is a rare neurological disorder with an incidence rate of 1-2 per 100,000 person-years. In July 2021, data from the Vaccine Adverse Event Reporting System (VAERS) indicated that more cases of GBS were being reported after vaccination with Ad.26.COV2.S in comparison to other mRNA vaccines.

On July 12, 2021, the U.S. FDA added a warning about GBS to the Ad.26.COV2.S vaccine fact sheet. GBS is being monitored in the Vaccine Safety Datalink as part of ongoing rapid and prospective COVID-19 vaccine safety surveillance efforts.

In a recent study published on the preprint server medRxiv*, researchers compiled available data from the interim analysis of the number of cases of GBS and the risks posed by different vaccines.

Study details

All relevant data for the current study were obtained from the Vaccine Safety Datalink, a collaboration between nine U.S. integrated healthcare systems and the U.S. Centers for Disease Control and Prevention (CDC).

Eight data-contributing organizations contributed data, including Kaiser Permanente in Colorado, Northern California, Northwest, Southern California, and Washington, Marshfield Clinic, HealthPartners, and Denver Health. All organizations had access to comprehensive medical records, including vaccinations for a total of 10,158,003 people over the age of 12 years as of November 10, 2021.

The current study analyzed vaccination data between December 13, 2020, through November 13, 2021. During this time, a total of 14,723,318 doses of COVID-19 vaccines were administered, including 467,126 doses of Ad.26.COV2.S, 8,573,823 doses of BNT162b2, and 5,682,369 doses of mRNA-1273. Eleven cases of GBS after Ad.26.COV2.S were confirmed.

Weekly analyses were used to compare the outcome incidence observed during a risk interval after vaccination between 1-21 days or 1-42 days with outcome incidence expected. The expected outcome incidence was derived from vaccinated comparators who were concurrently (on the same day) in a postvaccination comparison interval between 22-42 days or 43-84 days, respectively. Separate analyses were also obtained from unvaccinated comparators who were concurrently unvaccinated.

Timing of GBS Symptom Onset after COVID-19 Vaccination
Timing of GBS Symptom Onset after COVID-19 Vaccination

Patients who had received two doses of an mRNA vaccine were considered for analyses 1-21 days after dose 1 and again 1-21 days old after receiving their second dose. However, once they received dose 2, the follow-up time after dose 1 was censored; hence, most of the comparison time in the vaccinated concurrent comparator analyses was after dose 2.

This surveillance approach used two post-vaccination risk intervals, 1-21 days and 1-42 days. The 1-21 day risk interval allowed for on-time analyses and avoided bias introduced from the short interval between two mRNA vaccine doses. However, a 1-42 day risk interval was also used, as this was the standard interval used in vaccine safety studies of GBS and other outcomes.

Potential cases of GBS were identified using International Classification of Diseases 10th Revision (ICD10) code G61.0 in the emergency or inpatient setting, specifically when G61.0 first appeared in an individual’s record in the 1-84 day window after any COVID-19 vaccination.

Since disease onset may begin before a diagnosis is recorded in the medical record, potential cases with the ICD-10 code in the 85-98 day window after vaccination were also reviewed. After review, all cases underwent adjudication according to the Brighton Collaboration criteria.

The unadjusted incidence rate of confirmed cases of GBS per 100,000 person-years in the 1-21 days window post-Ad.26.COV2.S vaccination was 34.6, which is significantly higher than the background rate. The adjusted rate ratios (R.R.) in the 1-21 versus 22-42 day windows following Ad.26.COV2.S vaccination was 6.03.

Thirty-four cases of GBS were confirmed post mRNA vaccination. The unadjusted incidence rate of confirmed cases per 100,000 person-years in the 1-21 day window after administration of mRNA vaccines was 1.4, whereas the adjusted R.R. in the 1-21 versus 22-42 day windows following mRNA vaccination was 0.56. When comparing Ad.26.COV2.S and mRNA vaccinations, the adjusted R.R. was 20.56.


This interim analysis of surveillance data of COVID-19 vaccines demonstrates an elevated risk of GBS observed after primary Ad.26.COV2.S vaccination. There is ongoing surveillance, and more results are expected soon.

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources

Journal references:

Article Revisions

  • Jun 16 2023 - The preprint preliminary research paper that this article was based upon was accepted for publication in a peer-reviewed Scientific Journal. This article was edited accordingly to include a link to the final peer-reviewed paper, now shown in the sources section.
Sreetama Dutt

Written by

Sreetama Dutt

Sreetama Dutt has completed her B.Tech. in Biotechnology from SRM University in Chennai, India and holds an M.Sc. in Medical Microbiology from the University of Manchester, UK. Initially decided upon building her career in laboratory-based research, medical writing and communications happened to catch her when she least expected it. Of course, nothing is a coincidence.


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  1. lolaka lamnere lolaka lamnere United States says:

    The info in this article is misleading, you should update the beginning and state Pfizer is FDA approved not EUA anymore unless it’s for children. Also this article should just talk about Jansen and Jansen covid 19 vaccine which is not MRNA it’s made with traditional vaccine components using a disabled adenovirus. People are going to mistake this info for being with all vaccines and further make false fear due to it not being clear. If you can edit this I would say remove unnecessary names of vaccines that don’t pertain to the article.

  2. Justin Dougherty Justin Dougherty United States says:

    So. Serious life long side effects that they knew nothing about before mandating vaccines. What other effects are there that they maybe missed or more than likely just ignore....

    • unknownuser2808 unknownuser2808 United States says:

      Only 34 has reported vs 5billion people took have better odds not be 35 person

    • Emery Galambos Emery Galambos United States says:

      The likelihood of this is miniscule and relies on information from the VAERS database which is self-reported.

      If these odds scare you you should never drive nor take a shower as both are more likely to cause you harm than the J&J vaccine, which is the only one involved.  No incidence of this issue with either Moderna or Pfizer.

    • Kathleen R Kathleen R United States says:

      --  First of all, this article explains that previously, occurrences of Guillain-Barré syndrome were known to occur in people taking ONLY the Janssen (Ad.26.COV2.S) vaccine. The KNEW about this in JULY 2021. (not sure what made you think they 'knew nothing about this till now'.  It certainly wasn't from the article because they CITE the dates and info they had in July. You might want to brush up on your reading comprehension).
      -- Secondly, it was ONLY the Janssen vaccine.  SO take a different vaccine if you want.  
      --  Third, the occurrences were VERY RARE. 1-2 in every 100,000.  So, excellent odds for NOT getting it.  Now studies over the last 12 months show the occurrences seem to have risen to about 2.39 in every 100,000.   Still, excellent odds.  (99,997 did NOT get GBS after their Janssen vaccine.)

      -- Fourth:  MOST people recover from Guillain-Barré syndrome (GBS). 60% to 80% recover. Look it up.

      Fifth:  No one is requiring you to get a vaccine.  No one will hold you down and jam a needle in your arm.  You are only 'mandated' to get a vaccine if you want to interact with others in the world.  And this is NOT NEW.  You were required to be vaccinated to attend elementary school, and now you are are required to get vaccinated to attend concerts, and football games, and JOBS where you will likely interact with other co-workers and possibly, the public.  It is not new.  We've been doing this for decades.  Don't get vaccinated if you don't want, you can just stay home.  That is absolutely your choice.  But it is NOT your choice to NOT get vaccinated and potentially infect hundreds (maybe thousands) of OTHER INNOCENT PEOPLE. --

      • David Baez David Baez United States says:

        Companies are taking your refusal to get the vaccine as a letter of resignation just to avoid terminating and paying severance.
        To many people, choosing to get vaccinated verses being unemployed without pay is a threat.
        I'm not against people getting the vaccine, but I am against the madate and forcing a vsccine that still has not completed the study trials is unethical. We saw how the FDA approved Oxycodone with improper studies and the cities that suffered from it; and that was only 20yrs ago. Why should I trust that the FDA has not taken short cuts or if they themselves have been misinformed?

    • Adam Gallant Adam Gallant Canada says:

      Well, sure. We all know all medical intervention has side effects but it's a pros cons game.

      The odds of getting GBS from JJ is 0.02% (20 in 100,000).
      The odds you died of COVID-19 in the USA is 0.2% (800,000 deaths / 330,000,000) and counting.

      Now consider 70% of GBS sufferers fully recover, death is worse, and that COVID-19 comes with other severe side effects like lung, heart and brain scaring.

      I'll take the JJ (or the safer mRNA) shots and knowing choose a .006% (30% of .02%) chance of long term nerve damage over a .2% chance of Dead.

      • M Stevens M Stevens United States says:

        Your simplistic math needs to be adjusted for the following: the backward looking risk of death for the majority of Americans is far less than .2%, especially for those healthy and under say 50 or so, where the risk of death is minuscule. For the younger, healthy population it is not obvious that the unknown risks of the vaccine (it is not a vaccine btw, just like a flu shot isn't) is worth some protection against an extremely low risk outcome. It is a toss up for the not vulnerable and thus the choice should be there's to make.

    • Darood Sandstrom Darood Sandstrom Canada says:

      What won't make you a fear mongering dunce? 11 cases out of half a million people. Sounds like decent odds to me.

  3. melanie mccool melanie mccool United States says:

    As a survivor of childhood GBS, I am always afraid to get any vaccine that is ”live”. I did get both Pfizer’s and the booster knowing they were different. Any stats on vulnerability of those who previously had GBS? Are we more susceptible? Thanks for this article snd any help you have.

  4. Cyrus Stark Cyrus Stark United States says:

    This article is misleading for a few reasons. But the largest would be using VAERS as your source.

    VAERS, does not require claims to be verified. All the require is a statement, and a different part of the CDC follows up on it. VAERS does not require proof of causation, a different database in the CDC determines that.

    Using the VAERS database to gather results from, is intellectually dishonest.

  5. Paco Maco Paco Maco United States says:

    Can someone state this article in English? Basically is the link from all vaccines for covid? Or just johnson and johnson? The lack of normal terminology here is the reason people go nuts about vaccines. Just present it in easier to understand terms. We're not all doctors yo

  6. Iiam James everette Iiam James everette United States says:

    The problem with Covid-19 and Covid -19 Vaccinations isn't the Virus, or V
    vaccinations itself.   Its the ignored, unresolved historical evil murderous machinations of U.S. medicine, science,  politics, institutions and media.  You can't heal the people of a country when they are employees living inside the business for sale as a store.  U.S. Inc

  7. douglas denunzio douglas denunzio United States says:

    Omicron is hard to publish correct research on. Everyone has a different outcomes with the vaccines.

  8. Lee Diogeneia Lee Diogeneia United States says:

    Have to wonder if the author/outlet just wants to scare people. By all means, let's add to global vaccine hesitancy and confusion with incomplete and unvetted information.

    "What doesn't kill you mutates and tries again."

  9. Bijayananda Baisakh Bijayananda Baisakh India says:

    My father was also suffered from GBS after 24 hours of 1 st dose of covieshield taken in 16/03/2021, He was in mechanical ventilation for 50 days, after that he died on 08/05/2021. I have spent Rs 1300000/- but all in vain, who will responsible  for this? Now my liability is too high.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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