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Risk of Guillain-Barré syndrome after COVID-19 vaccines was low overall, but unusually high after the Johnson & Johnson shot, surveillance data showed.

Among 15.1 million doses of COVID-19 vaccines included in the Vaccine Safety Datalink, the unadjusted incidence rate of confirmed Guillain-Barré syndrome 1 to 21 days after receiving the Johnson & Johnson vaccine was 32.4 per 100,000 person-years, significantly higher than the background rate, reported Nicola Klein, MD, PhD, of Kaiser Permanente Northern California in Oakland, and colleagues.

The unadjusted incidence rate of confirmed Guillain-Barré 1 to 21 days after mRNA vaccines was 1.3 per 100,000 person-years, similar to the background rate, they wrote in .

"The background rate for Guillain-Barré syndrome is known to be about one or two cases per 100,000 person-years," Klein told 名媛直播.

The findings confirm data seen in the Vaccine Adverse Event Reporting System that led to the FDA warning about the Johnson & Johnson vaccine in July 2021.

"The Vaccine Safety Datalink is an active surveillance system for vaccine safety events, complementary to VAERS but quite different," Klein noted.

"In the Vaccine Safety Datalink, eight integrated health systems contribute data in collaboration with the CDC," she said. "We have full access to complete medical records and we can actively survey for all sorts of medical encounters and health events after vaccination. We know our underlying population; we know who is in the denominator and we don't have to make estimates."

The study evaluated data from 7.9 million people, ages 12 and older, who received either the Johnson & Johnson shot or a Pfizer-BioNTech or Moderna vaccine (including mRNA vaccine doses 1 and 2) from December 2020 to November 2021. The outcome was Guillain-Barré syndrome with symptom onset after vaccination, confirmed by medical record review.

"We pre-specified that we would look at the charts of all the Guillain-Barré syndrome cases after vaccination," Klein said. "The charts were all reviewed and adjudicated by neurologists and other medical professionals."

Overall, 15,120,073 COVID-19 vaccine doses were administered to 7,894,989 individuals, including 483,053 Johnson & Johnson, 8,806,595 Pfizer, and 5,830,425 Moderna doses. Patients had a mean age of 46.5 and 53.8% of doses were received by women. Rate ratios (RRs) comparing Guillain-Barré risk after vaccination were adjusted for age, sex, race and ethnicity, site, and calendar day.

Eleven cases of Guillain-Barré syndrome were confirmed after the Johnson & Johnson shot. The adjusted RR in days 1 to 21 compared with days 22 to 42 after the Johnson & Johnson vaccine was 6.03 (95% CI 0.79-147.79).

Thirty-six cases of Guillain-Barré after mRNA vaccines were confirmed; the adjusted RR in days 1 to 21 versus days 22 to 42 was 0.56 (95% CI 0.21-1.48) for the mRNA vaccines.

A head-to-head comparison showed the Johnson & Johnson vaccine carried a 20% higher risk for Guillain-Barré than the mRNA shots (adjusted RR 20.56, 95% CI 6.94-64.66). Using a risk interval of 1 to 42 days, the adjusted RR dropped to 11.46 (95% CI 4.83-26.16, P<0.001).

The study had several limitations, the researchers acknowledged. Many fewer doses of the Johnson & Johnson vaccine were administered, leading to reduced statistical power and wide confidence intervals. People who received the Johnson & Johnson shot may have differed from others in ways that might affect Guillain-Barré risk. In addition, the incidence of confirmed Guillain-Barré during the COVID-19 pandemic has not been established and may differ from pre-pandemic background rates.

Surveillance for Guillain-Barré in the Vaccine Safety Datalink is ongoing, Klein noted. In December 2021, the CDC recommended Pfizer and Moderna's COVID-19 vaccines over Johnson & Johnson's for all adults.

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