The initial 12 US cases of Cerebral Venous Sinus (CVST) with thrombocytopenia after Ad26.COV2.S (Janssen/Johnson & Johnson) vaccination represent serious events. This case series may inform clinical guidance as Ad26.COV2.S vaccination resumes in the US as well as investigations into the potential relationship between Ad26.COV2.S vaccine and CVST with thrombocytopenia.

Patients’ ages ranged from 18 to younger than 60 years; all were White women, reported from 11 states.

7 patients had at least 1 CVST risk factor, including obesity (n = 6), hypothyroidism (n = 1), and oral contraceptive use (n = 1); none had documented prior heparin exposure.

Time from Ad26.COV2.S vaccination to symptom onset ranged from 6 to 15 days.

11 patients initially presented with headache; 1 patient initially presented with back pain and later developed headache.

Of the 12 patients with CVST, 7 also had intracerebral hemorrhage; 8 had non-CVST thromboses.

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