The FDA and CDC have elected to pause the JJJ vaccine’s rollout in the US; The most detailed and thorough information I could find on the matter is discussed in a media call between Drs. Woodcock, Schuchat, and Marks.

Here’s my summary:

• Vaccinations have been paused for the JJJ vaccine after six reported cases of CVSTs (cerebral venous sinus thromboses) with thrombocytopenia. In this time period, 6.8 million doses have been administered, thus the risk would be less than 1 per million as of right now.

• The mechanism for this phenomenon is not fully understood currently, but is thought to be due to an inappropriate immune response directed against platelets or elements of the coagulation cascade. 

• 0 cases of this phenomenon have been noted with either mRNA vaccine. 

• The background rate of cerebral venous thrombosis which is thought to be 2 to 14 per million person-years. However, the co-occurrence with thrombocytopenia is what makes this a signal, per Peter Marks. We are not aware of a background rate for this combination of thrombocytopenia and CVSTs. This does occur very rarely as an autoimmune phenomenon but no annualized rate (how many cases per people per year) is known. 

• The pause is a recommendation but it is not binding. Patients may still receive this vaccine right now if a qualified healthcare professional determines it to be appropriate and if the state elects to continue vaccination with it. 

• Marks implies that this is important to make clinicians aware because standard treatments for the clots may worsen this disease.

• The cases are occurring almost exclusively in women < 50 but no association with OCPs has been confirmed. 

• Pre-existing comorbidities in these patients were not universally present; limited case numbers make generalizations about risk factors difficult. 

• A single case of CVST in a vaccine recipient was noted in JJJ’s clinical trial- it was not associated with thrombocytopenia, however.

• JJJ’s 2 dose trial is still currently occurring- there will be a communication later today about what actions they may take in view of this pause.

• This occurs at least 6 days after vaccines but less than 3 weeks- median = 9 days. A headache very shortly after vaccination is a normal aspect of reactogenicity; severe headache within that specified interval should result in a differential diagnosis that considers VITT, especially in combination with other symptoms of disseminated coagulopathy e.g. abdominal pain, shortness of breath, leg pain. 

• Fact sheets for the vaccine will be updated regarding this putative risk.

• There are too few cases of this phenomenon to conclude it is due to adenovirus vectors or any other risk factors.