Over 14 months, GBS reporting rates within 21 and 42 days of administration of Janssen’s replication-incompetent adenoviral vector vaccine were approximately 9 to 12 times higher than after administration of the Pfizer-BioNTech (BNT162b2) or the Moderna (mRNA-1273) mRNA COVID vaccines.
Additionally, observed GBS cases after the Janssen shot were 2 to 3 times greater than expected, based on background rates within 21 and 42 days of vaccination.
Conversely, and confirming prior data, there was no increased risk for GBS with the Pfizer or Moderna vaccines and no significant difference between observed and expected numbers of GBS cases after either mRNA COVID-19 vaccine.
The findings were published online in JAMA Network Open.
More precise risk estimates
Winston Abara, MD, with the U.S. Centers for Disease Control and Prevention, and colleagues analyzed GBS reports submitted to the VAERS between December 2020 and January 2022.
Among 487.6 million COVID-19 vaccine doses administered, 3.7% were Janssen’s Ad26.COV2.S vaccine, 54.7% were Pfizer’s BNT162b2 vaccine, and 41.6% were Moderna’s mRNA-1273 vaccine.
There were 295 verified reports of GBS identified after COVID-19 vaccination. Of these, 209 occurred within 21 days of vaccination and 253 within 42 days.
Within 21 days of vaccination, GBS reporting rates per 1 million doses were 3.29 for the Janssen vaccine versus 0.29 and 0.35 for the Pfizer and Moderna vaccines, respectively. Within 42 days of vaccination, reporting rates per 1 million doses were 4.07, 0.34, and 0.44, respectively.
Also within 21 days of vaccination, GBS reporting rates were significantly higher with the Janssen vaccine than the Pfizer vaccine (reporting rate ratio, 11.40) and the Moderna vaccine (RRR, 9.26). Similar findings were observed within 42 days after vaccination.
The observed-to-expected ratios were 3.79 for 21-day and 2.34 for 42-day intervals after receipt of the Janssen vaccine, and less than 1 (not significant) after the Pfizer or Moderna vaccine within both post-vaccination periods.
“Unlike prior studies, our analysis included all U.S. reports of verified GBS cases that met the Brighton Collaboration GBS case definition criteria (Brighton Levels 1, 2, and 3) submitted over a 14-month surveillance period to the to the Vaccine Adverse Event Reporting System,” Dr. Abara said in an interview. “Because we used all U.S. reports, the sample of verified GBS cases in this analysis is larger than other studies. Therefore, it may provide a more precise estimate of the GBS risk within 21 and 42 days after mRNA and Ad26.COV2.S vaccination,” he said.
‘Remarkably low’ use
Nicola Klein, MD, PhD, Kaiser Permanente Vaccine Study Center, Oakland, Calif., noted that this is a “nice confirmatory analysis that supports and further expands what’s been observed before.”
Last year, as reported by this news organization, Dr. Klein and colleagues reported data from the Vaccine Safety Datalink confirming a small but statistically significant increased risk for GBS in the 3 weeks after receipt of the Janssen COVID-19 vaccine but not the Pfizer or Moderna vaccines.
Unlike VAERS, the Vaccine Safety Datalink is not a reporting system. It’s an active surveillance of medical records in the Kaiser Permanente system. The VAERS is a passive system, so it requires individuals to report GBS cases to the VAERS team, Dr. Klein explained.
So although the two studies are slightly different, overall, the VAERS data is “consistent with what we found,” she said.
Also weighing in, C. Buddy Creech, MD, MPH, director of the Vanderbilt Vaccine Research Program and professor of pediatrics at the Vanderbilt University School of Medicine, Nashville, Tenn., said it is “important to realize that GBS had been observed after adenovirus-vectored vaccines earlier in the pandemic, both for the AstraZeneca vaccine and the Janssen vaccine.”
The Advisory Committee on Immunization Practices (ACIP) preferentially recommends that people age 18 years and older receive an mRNA COVID-19 vaccine rather than the Janssen adenoviral vector vaccine when both types of COVID-19 vaccine are available.
“Thus, the use of the Janssen vaccine is remarkably low in the U.S. right now,” Dr. Creech said.
“Nevertheless, we have a firm commitment, both scientifically and ethically, to track potential side effects after vaccination and to make sure that the vaccines in use for COVID, and other important infectious diseases, are safe and effective,” he added.
The study had no commercial funding. Dr. Abara and Dr. Creech have reported no relevant financial relationships. Dr. Klein reported having received grants from Pfizer research support for a COVID vaccine clinical trial, as well as grants from Merck, GlaxoSmithKline, Sanofi Pasteur, and Protein Science (now Sanofi Pasteur).
A version of this article first appeared on Medscape.com.