Emily Jane Woo, MD, MPH; Adamma Mba-Jonas, MD, MPH; Rositsa B. Dimova, PhD; Meghna Alimchandani, MD; Craig E. Zinderman, MD, MPH; Narayan Nair, MD
IMPORTANCE As part of postauthorization safety surveillance, the US Food and Drug
Administration (FDA) has identified a potential safety concern for Guillain-Barré syndrome
(GBS) following receipt of the Ad26.COV2.S (Janssen/Johnson & Johnson) COVID-19 vaccine.
OBJECTIVE To assess reports of GBS received in the Vaccine Adverse Event Reporting System
(VAERS) following Ad26.COV2.S vaccination.
DESIGN, SETTING, AND PARTICIPANTS Reports of presumptive GBS were identified in
a US passive reporting system (VAERS) February-July 2021 and characterized, including
demographics, clinical characteristics, and relevant medical history.
EXPOSURES Receipt of the Ad26.COV2.S vaccine; the comparator was the background rate of
GBS in the general (unvaccinated) population that had been estimated and published based
on a standardized case definition.
MAIN OUTCOMES AND MEASURES Presumptive GBS; the reporting rate was analyzed,
including calculation of the observed to expected ratio based on background rates and
vaccine administration data. Because of limited availability of medical records, cases were not
assessed according to the Brighton Collaboration criteria for GBS.
RESULTS As of July 24, 2021, 130 reports of presumptive GBS were identified in VAERS
following Ad26.COV2.S vaccination (median age, 56 years; IQR, 45-62 years; 111 individuals
[86.0%] were < 65 years; 77 men [59.7%]). The median time to onset of GBS following
vaccination was 13 days (IQR, 10-18 days), with 105 cases (81.4%) beginning within 21 days
and 123 (95.3%) within 42 days. One hundred twenty-one reports (93.1%) were serious,
including 1 death. With approximately 13 209 858 doses of vaccine administered to adults in
the US, the estimated crude reporting rate was 1 case of GBS per 100 000 doses
administered. The overall estimated observed to expected rate ratio was 4.18 (95% CI,
3.47-4.98) for the 42-day window, and in the worst-case scenario analysis for adults 18 years
or older, corresponded to an estimated absolute rate increase of 6.36 per 100 000
person-years (based on a rate of approximately 8.36 cases per 100 000 person years [123
cases per 1 472 162 person years] compared with a background rate of approximately 2 cases
per 100 000 person years). For both risk windows, the observed to expected rate ratio was
elevated in all age groups except individuals aged 18 through 29 years.
CONCLUSIONS AND RELEVANCE These findings suggest a potential small but statistically
significant safety concern for Guillain-Barré syndrome following receipt of the Ad26.COV2.S
vaccine. However, the findings are subject to the limitations of passive reporting systems and
presumptive case definition, and they must be considered preliminary pending analysis ofmedical records to establish a definitive diag