The Janssen vaccine (Ad26.COV2.S) is a replication-incompetent adenoviral vector vaccine.
The data show no increased risk of GBS with the Pfizer (BNT162b2) or Moderna (mRNA-1273) shots – both mRNA vaccines.
“Our findings support the current guidance from U.S. health officials that preferentially recommend use of mRNA COVID-19 vaccines for primary and booster doses,” Nicola Klein, MD, PhD, with Kaiser Permanente Vaccine Study Center, Oakland, Calif., told this news organization.
“Individuals who choose to receive Janssen/J&J COVID-19 vaccine should be informed of the potential safety risks, including GBS,” Dr. Klein said.
The study was published online in JAMA Network Open.
Between mid-December 2020 and mid-November 2021, roughly 15.1 million doses of COVID-19 vaccine were administered to nearly 7.9 million adults in the United States.
This includes roughly 483,000 doses of the Janssen vaccine, 8.8 million doses of the Pfizer vaccine, and 5.8 million doses of the Moderna vaccine.
The researchers confirmed 11 cases of GBS after the Janssen vaccine.
The unadjusted incidence of GBS (per 100,000 person-years) was 32.4 in the first 21 days after the Janssen vaccine – substantially higher than the expected background rate of 1 to 2 cases per 100,000 person-years.
There were 36 confirmed cases of GBS after mRNA vaccines. The unadjusted incidence in the first 21 days after mRNA vaccination was 1.3 per 100,000 person-years, similar to the overall expected background rate.
In an adjusted head-to-head comparison, GBS incidence during the 21 days after receipt of the Janssen vaccine was 20.6 times higher than the GBS incidence during the 21 days after the Pfizer or Moderna mRNA vaccines, amounting to 15.5 excess cases per million Janssen vaccine recipients.
Most cases of GBS after the Janssen vaccine occurred during the 1- to 21-day risk interval, with the period of greatest risk in the 1-14 days after vaccination.
The findings of this analysis of surveillance data of COVID-19 vaccines are “consistent with an elevated risk of GBS after primary Ad26.COV2.S vaccination,” the authors wrote.
The researchers note that nearly all individuals who developed GBS after the Janssen vaccine had facial weakness or paralysis, in addition to weakness and decreased reflexes in the limbs, suggesting that the presentation of GBS after COVID-19 adenoviral vector vaccine may be novel.
“More research is needed to determine if the presentation of GBS after adenoviral vector vaccine differs from GBS after other exposures such as Campylobacter jejuni, and to investigate the mechanism for how adenoviral vector vaccines may cause GBS,” Dr. Klein and colleagues said.
“The Vaccine Safety Datalink continues to conduct safety surveillance for all COVID-19 vaccines, including monitoring for GBS and other serious health outcomes after vaccination,” Dr. Klein said in an interview.
This study was supported by the Centers for Disease Control and Prevention. Dr. Klein reported receiving grants from Pfizer research support for a COVID vaccine clinical trial as well as other unrelated studies, grants from Merck, grants from GlaxoSmithKline, grants from Sanofi Pasteur, and grants from Protein Science (now Sanofi Pasteur) outside the submitted work.
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