Thread by @MonicaGandhi9

Rare side effect after J&J vaccine. 6 cases of blood clot called cerebral venous sinus thrombosis (CVST) among women between the ages of 18-48, with symptoms between 6-13 days after vaccination. Out of 6.8 million doses given (0.00009%). U.S. pausing statnews.com/2021/04/13/u-s…

222 cases of CVST out of 34 million people with AztraZeneca vaccine reported as well (0.00006%), most cases in women under 55 years. Of note, both J&J vaccine and AZ vaccine are adenovirus vaccines with DNA coding for spike protein inside them.
sciencemag.org/news/2021/04/h…

Both extremely rare (0.0000006-0.000009) so please first keep that in mind. Postulated mechanism here - syndrome called vaccination immune thrombotic thrombocytopenia (VITT). All patients with low platelets (thrombocytopenia) & unusual clots (thrombosis).
nejm.org/doi/full/10.10…

Vaccine seems to trigger platelet factor 4 (PF4)–heparin antibodies; something we rarely see heparin (a blood thinner) do- trigger these antibodies. Known that adenovirus can bind to platelets & cause platelet activation; leads to both low platelets & some to clump (clot)

Alternatively, possible trigger of these PF4-reactive antibodies could be free DNA in vax. Can diagnosis with anti-PF4 antibodies. Very rare; don't worry if you have already received J&J; CDC & FDA recommending halting J&J for now while being investigated; sorry to report this

Extremely rare side effects; seems to be restricted to younger and mostly women; Europe continues to give to older individuals (>60); the benefit of vaccination for a life-threatening pandemic is indisputable; maybe instead restrict use to older & further evaluate

Want to put this in perspective. Like breakthroughs after vax, this side effect is EXTREMELY rare & COVID-19 not rare in places like Michigan (where hospitalization rate is turning- will tweet) so think risk-benefit on decisions. Keep calm; we have to get through pandemic too

I think this is a wonderful visualization about the risk-benefit calculus of the J&J vaccine by @WaPo. Look at red dots of 1 in 1.1 million vaccines rare side effect; "By way of comparison, every year about 12 in 100,000 Americans die in a car crash
washingtonpost.com/politics/2021/…

And then finally, I believe committee looking into whether the dose the J&J vaccine used is too high (and AZ vaccine too). Please remember phase I/II trials of escalating doses; sometimes we choose the highest dose when medium/low work as well - see graph
nejm.org/doi/full/10.10…