Apr 9, 2021 Available evidence does not support causal inference Clinical details of a participant in a Covid-19 vaccine trial who developed Guillain-Barré syndrome (GBS) after vaccination were published in Two cases of GBS, one in the active and one in the placebo arm, were reported in the Ad26.COV2.S (Johnson & Johnson) Covid-19 vaccine trial data. “Our patient in the vaccine arm did not have any clinical features differentiating her from patients with typical GBS,” wrote Anthony Amato, MD, and co-authors, all of Brigham and Women’s Hospital, Boston. “From the available evidence, it is not possible to draw causal inferences about the association of Covid-19 vaccination and the development of GBS,” they added.