GBS: ‘Adverse event of interest’
A link between modern vaccines and GBS first appeared in the 1970s with the hastily developed swine flu vaccine. “In late 1976,” Dr. Lunn explained, “it was identified that patients who were given that vaccine seemed to be developing illnesses consistent with GBS.” By 1980, Dr. Lunn said, the risk level was determined to be only five or six cases for every 1 million doses of vaccine administered. “But the vaccine program was aborted, and swine flu never really happened.” Every year since, “there has been a surveillance program looking at the occurrence of an association of GBS with influenza vaccine.”
Minor fluctuations aside, he said, the overall incidence of GBS with influenza vaccination – 1 GBS case for every 1 million vaccine doses given – has remained consistent over several decades. “Nevertheless, GBS became an adverse event of special interest for any vaccination campaign.”
COVID-19 vaccination. Dr. Lunn and colleagues used the United Kingdom National Health Service (NHS) National Immunoglobulin Database, and other databases, to pinpoint the risk of GBS presented by the first dose of the AstraZeneca ChAdOx1 nCoV-19 adenoviral vaccine.10 As with U.K. GBS cases, every COVID-19 vaccination is linked to an NHS number. “We identified all the cases of GBS, found their NHS numbers, and went back and found the exact dates they’d been vaccinated, and with which vaccine.” Only the adenoviral-vector vaccine carried an excess risk of GBS – 5.8 cases for every 1 million doses, associated only with the first dose and peaking at approximately 25 days post vaccination – compared with other vaccines used in the United Kingdom.
Researchers looked at data from the Vaccine Adverse Event Reporting System (VAERS), a program of the Centers for Disease Control and Prevention and the Food and Drug Administration, encompassing nearly 500 million COVID-19 vaccine doses given between December 2020 and January 2022. They found that patients who received the Ad26.COV2.S vaccine (Janssen/Johnson & Johnson) had a rate of GBS (within 21 and 41 days post vaccination) that was 9 and 12 times higher, respectively, than corresponding rates for the mRNA-1273 (Moderna) and BNT162b2 (Pfizer BioNTech) COVID-19 vaccines.11 Risk was distributed relatively evenly by gender and age. Also at day 21 and day 41, observed event ratios with the adenoviral-vector vaccine (use of which has been suspended in the United States) were 3.79 and 2.34, respectively. Observed-event ratios with the other vaccines mirrored expected background rates.
The VAERS analysis confirms earlier data from the CDC’s Vaccine Safety Datalink, which showed that, among approximately 15 million U.S. vaccine doses given between mid-December 2020 and mid-November 2021, the unadjusted GBS incidence rate for every 100,000 person-years for the adenoviral vaccine, 21 days post exposure, was 32.4, compared with 1.3 for the mRNA vaccine. The adjusted relative risk with the adenoviral vaccine in the first 3 weeks post vaccination, compared to the 3- to 6-week interval post vaccination, was 6.03.12 In addition, a head-to-head comparison of adenoviral versus mRNA vaccines at 21 days revealed an adjusted rate ratio of 20.56. Mechanistically, some experts theorize that antibodies induced by the Janssen vaccine might cross-react with glycoproteins on the myelin sheath of peripheral nerve axons to cause GBS, but this remains unproven.11
The AstraZeneca vaccine uses a chimpanzee adenovirus; the Janssen vaccine uses a human adenoviral carrier. “The only commonality between the Janssen/Johnson & Johnson and AstraZeneca vaccines, and the only thing that’s different from the other vaccines, is the adenoviral vector packaging,” Dr. Lunn emphasized. “I believe it’s what generates GBS after COVID-19 vaccination. It has nothing to do with the COVID-19 vaccination, the spike protein, the nucleic acid, the DNA, or anything else.”
The adenoviral vector probably also explains why GBS peaks during winter, said Dr. Lunn. “That’s when adenovirus is circulating.” When people contract the common cold, he explained, they don’t visit their family physician and request a swab to isolate the adenovirus. “By the time you get GBS, the adenovirus has been cleared. We’ve all got antibodies to adenovirus all over the place, anyway, because we get it so often.”
It would be difficult to prove conclusively that adenovirus belongs on the list of GBS causes, Dr. Lunn allowed. “But I have a strong suspicion that it does. COVID-19 and COVID-19 vaccination have given us some new avenues into identifying GBS causation potentially in the near future.” More research is needed in this area, he said.
Dr. Lunn has been a principal investigator for argenx (efgartigimod) and an adviser to AstraZeneca (ChAdOx1 nCoV-19). He has received travel grants from CSL Behring.