AstraZeneca COVID-19 vaccine and blood clots – let’s go for facts first

ext up on the COVID-19 vaccine hit list is that the AstraZeneca (Oxford University) vaccine causing blood clots (thrombus). Spoiler alert – no it probably doesn’t.

We should just assume that every single “adverse event” whether or not they’re actually linked to any COVID-19 vaccine will involve the post hoc ergo propter hoc fallacy, which states that because one event precedes another event, they must be linked. In this case, are blood clots related to the AstraZeneca COVID-19 vaccine?

Spoiler alert – the answer is no. That would make this a short article, but real science requires real explanation, so here we go.

To put this into some perspective, let’s do the math:

• For deep vein thrombosis, that means the observed risk after the AstraZeneca COVID-19 vaccines is 0.88 per 1 million vaccinated individuals.
• For pulmonary embolism, the observed risk would be around 1.29 per 1 million vaccinated individuals.
• The overall risk of these two types of blood clot events is about 1 in 1000 in the general population, substantially higher than the “risk” after the AstraZeneca COVID-19 vaccine. I’m not saying that getting the vaccine prevents blood clots, but a bad use of statistics would lead one to such a conclusion.

So far, the large, well-controlled clinical trials for the AstraZeneca and JNJ (which is also based on adenovirus vector technology) have not shown any increased risk for blood clots.

Yes, the SARS-CoV-2 virus seems to cause thrombi in many patients, which might lead one to think there is some biological plausibility to the blood clot issue. However, no live virus is used in the Pfizer, Moderna, JNJ, and AstraZeneca vaccines. All four of these vaccines induce the production of one small part of the virus, the spike protein, for a limited time. A real infection by SARS-CoV-2 will have billions of viruses all replicating and causing havoc to the body.

Finally, we don’t have any information on these 37 patients – are there confounders like high risk for blood clots, such as smoking, obesity, diabetes, and other comorbidities for thrombus? Those may be more important to the risk of clots than the AstraZeneca vaccine, and that’s why we investigate each claim to determine if there is a potential link.

https://www.skepticalraptor.com/skepticalraptorblog.php/astrazeneca-covid-19-vaccine-and-blood-clots-lets-go-for-facts-first/