The six cases in the U.S. were in women between the ages of 18 and 48. Women have been disproportionately affected by both vaccines.
The blood-clotting disorder is called cerebral venous sinus thrombosis, and it was only reported in individuals who also had low levels of blood platelets, a condition called thrombocytopenia.
The Johnson & Johnson and AstraZeneca COVID-19 vaccines are both adenovirus viral vector-based vaccines with similar mechanism.
No thrombotic syndrome cases have been reported in people who have received either the Pfizer Inc. PFE, or Moderna Inc. MRNA, mRNA vaccines.