The incidence of Guillain-Barré syndrome (GBS) is increased after Ad.26.COV2.S vaccination, but incidence is not increased after mRNA vaccination, according to a study published online April 26 in JAMA Network Open.

Kayla E. Hanson, MPH, from the Marshfield Clinic Research Institute in Wisconsin, and colleagues used data from the Vaccine Safety Datalink to describe the incidence of GBS following COVID-19 vaccination. Data were included for 10,158,003 participants who were aged 12 years or older.

From Dec. 13, 2020, through Nov. 13, 2021, 15,120,073 doses of COVID-19 vaccine were administered to 7,894,989 individuals, including 483,053 Ad.26.COV2.S doses, 8,806,595 BNT162b2 doses, and 5,830,425 mRNA-1273 doses. The researchers confirmed 11 cases of GBS after Ad.26.COV2.S vaccination. The unadjusted incidence rate of GBS was 32.4 per 100,000 person-years in the one to 21 days after Ad.26.COV2.S, which was significantly higher than the background rate; the adjusted rate ratio was 6.03 in the one to 21 versus 22 to 42 days following Ad.26.COV2.S vaccination. There were 36 confirmed cases of GBS after mRNA vaccines, for an unadjusted incidence rate of 1.3 per 100,000 in the one to 21 days after vaccination. The adjusted rate ratio was 0.56 in the one to 21 versus 22 to 42 days after vaccination. The adjusted rate ratio was 20.56 in a head-to-head comparison of Ad.26.COV2.S versus mRNA vaccines.

"In this interim analysis of surveillance data of COVID-19 vaccines, findings were consistent with an elevated risk of GBS after primary Ad.26.COV2.S vaccination," the authors write.

Several authors disclosed financial ties to the pharmaceutical industry, including receipt of grants from manufacturers of COVID-19 vaccines; one author disclosed ties to Arnold Ventures.