Vaccine associated thrombocytopenic thrombosis from the eyes of general practice - a thread 🧵
#CovidVaccine #AZ
The JCVI announcement today recommends to offer alternative #CovidVaccine to AZ in healthy adults < 30 years old (i.e. no underlying health conditions):…
This is following investigation into a blood clotting phenomenon DISTINCT from typical #VTE but clinically similar to heparin-induced thrombocytopenia (HIT) associated with thrombocytopenia and unusual site thrombosis (with a preponderance for CVST) post-AZ vaccination
Cases were first characterised in Germany here:… (preprint) describing the immunological basis for clotting i.e. PF4 antibodies --> ⬆️⬆️⬆️D-dimer, thrombocytopenia and ⬇️fibrinogen, disproportionately presenting in young patients
Interim / "living" guidance has since been published on the recognition and best management of probable cases:……
Although serious, this phenomenon is rare, estimated by the MHRA to be 4/1,000,000 persons vaccinated in the UK…
To provide some context, the risk of a healthy individual developing a blood clot on a 4+ hour flight is estimated to be 1/6000 i.e. approximately 42 x more likely than developing vaccine associated thrombocytopenic thrombosis…
Further to the biochemical distinction of this syndrome from typical VTE, there is no apparent association of the AZ vaccine with rates of typical VTE as described in this letter:…
The JCVI suggestion to defer vaccination for healthy <30 year-olds in favour of awaiting a non-AZ option is beautifully summarised in @alex_freeman slides, noting the *current* risk posed by COVID to these individuals is low enough to warrant this:…
Context is everything: Note that the risk / benefit changes in the event of another wave of COVID due to exposure risk:
This is the same principle for pausing the new AZ study in children: the risk of hospitalisation & death from COVID in children remains very low, and thus the need for mass vaccination is not as pressing, allowing time for further investigation:
⬆️Age and/or presence of certain comorbidities is linked with ⬆️risk of hospitalisation due to COVID. It should be borne in mind that hospitalisation with COVID carries a high risk of thrombosis, with an estimated prevalence of 17.4%:
As such, for the majority of patients we are currently vaccinating, the benefits outweigh the risks:…
Information to provide to patients - red flags to seek urgent medical advice. Note that post-vaccination headache is common (~50%); the emphasis is on those developing 4 or more days post-vaccination +/- symptoms as below
Currently, the @MHRAgovuk recommend that anyone in whom a first dose of AZ has been given without incident should continue to come forward for their 2nd dose when they are due.
What I cannot get my head around is the @MHRAgovuk precautionary advice regarding individuals with increased thrombosis risk. Considering the above, this does not appear to be an independent risk factor. Can any experts explain this for me? @bhwords @ProfMakris @karenbr001
Ask and you shall receive, although it seems unlikely PHE answered this just for me. Either way, a much more measured selection of conditions for exclusion/caution of AZ vaccine here:…
Still not convinced re: inherited thrombophilia...

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