AstraZeneca approval in the US

The risk is likely somewhere around 1 in 100,000. No medicine has had testing in trials that would reveal that rare of a risk. All new medicines have a chance of this kind of side effect showing up when it enters the market. Unless you are in your 20s and in an extremely low risk area for Covid, or are totally isolating with your entire household, you are almost certainly better off getting whatever vaccine is available to you.

People deserve information to make informed decisions, so I support a short pause in the US for that and the other reasons I mentioned. But if someone declined vaccination at all, or puts off vaccination for months until there’s a longer track record for the vaccines, they are making the wrong bet.

Even the risk band charts that have been posted are about risk of Covid per 12 weeks. The shot is a one-time risk for long-term protection against Covid and all of its consequences (not just death). (All DVST incidents so far have been from the first shot.).

This is complicated, and worth discussing with one’s doctor if there are concerns, but one liners like, “I don’t want to be a beta tester” do not capture a valid reason to delay vaccination.

The problem that’s been documented isn’t clots outside of the circulatory system, it’s cerebral venous sinus thrombosis seen in combination with low levels of blood platelets.

This is a clot in the vessels that normally drain blood from the brain. (per the embedded wikipedia link)

So the blood-brain barrier isn’t really relevant here. And fyi, the wikipedia article lists the common causes as

(bolding added)

I don’t believe the form you get from estrogen-containing birth control pills is associated with low platelets. But I think it can still be deadly.

Rummaging around, trying to find a summary of all VITT cases (I failed) I came across something called Brief19 - so far as I can tell it hasn’t been posted here before; if it has I apologize. But it looks very useful - here it is:

Doesn’t that just sound like the sort of thing we’ve been crying out for?

Its immediate relevance to this thread is this summary:

From which:

The upshot is that in a few instances, the AstraZeneca/Oxford vaccine appears to be causing a condition now being called “vaccine-induced immune thrombotic thrombocytopenia,” or VITT. That’s science jargon for: the vaccine can cause an immune reaction that lowers platelet counts which can potentially cause or worsen dangerous blood clot formation. To some, this might sound paradoxical. After all, platelets help us make blood clots. Why would a condition that lowers platelet levels cause more clots? The answer is that when platelets are attacked by the immune system, the platelets release particles—a kind of molecular shrapnel—which then cause blood clots to form or worsen. These blood clots can be harmless and sub-clinical, or they occur or travel to areas of the body where they can do great harm by literally blocking the rest of the blood from reaching its intended destination. In the lungs, large blood clots inhibit the rest of the blood from getting oxygen. In the brain, blood clots stop blood from returning to the heart. The ensuing traffic jam first causes damage around the veins where they occur, but eventually cause a stroke, because oxygenated blood eventually can’t reach that part of the brain. The reason that scientists worked this new vaccine-related phenomenon out so quickly is that this condition appears to be related to another similar and well-known problem, caused by a medication called heparin, a commonly used blood thinner.

Now that, I think, was useful.




Good resource, huh?

I think I’d better cross-post to the breaking news thread, where more people will see it.


Very good source, thank you.

Just forwarded it to my housemate who I drove to get J and J vaccine Saturday. 24 hours later she started the period from hell more than a week early. Now it seems that a temporarily debilitating period is not so bad considering. She’s 32 , so prime age for a VITT. Scary, but at least she’s under 24 hour observation by a trained nurse.

Jeez, that is scary. Fingers crossed for her.


LOL – nice. And I hope all goes well for her.

@Treppenwitz thanks for posting that link. It looks incredibly informative, and useful for sending people links. Bookmarking now.

(I had that very question about low platelet blood clots…)

An outline of the technical details on the probable clotting mechanism may be found here,

with more details in the referenced paper here, see the “Discussion” section:

Yes but the audience isn’t the choir. Many of these people have already had covid and don’t see the need.

This has to be sold to the public.

More cases found. 41 more cases, with 9 more deaths.

The UK is now considering raising the AZ age to over 40 rather than over 30.

Also, there was a question about this earlier:

Four cases of rare clotting were reported following a second dose, but the MHRA did not say how many second doses had been given.

Thanks, I had missed that. Checking back, this had been reported by a few news sources in the UK, but not so emphatically that it rose far above background noise.


By the end of March the total of cases was 79 (19 dead)
By (some time before) the end of April the total of cases was 209 (41 dead)

It’s hard to know how to interpret that - obviously, even without checking vaccination numbers at those dates, between end March and (near) end April this rise in case numbers is disproportionately large - too large to be accounted for simply by additional vaccinations. I can think of a few ways this could arise:

  • A genuinely much higher risk in a younger populations which have only recently been exposed to the vaccine (though this should be offset by current advice to seek alternatives if you are under 30)
  • Increased vigilance meaning fewer cases are now being missed
  • Historic cases being reviewed and reinterpreted
  • Historic cases simply being identified properly for the first time

There are likely other factors which could contribute. What we need is a decent review article in a medical journal - I’ll keep an eye on Brief19.


I could be wrong, but I thought these were all “historical” cases. Meaning ones that had previously been missed. I’ll take another look – I may be misremembering or interpreting.

ETA: OK, it’s just an implication that some (not all) of them are historical:

There were 41 deaths following the clots in Britain, the MHRA said, an increase of 9 from last week’s figures, although experts say historic cases might still be feeding through to the totals, and the clots are set to remain a rare event.

(Ugh, not “historic.” Historical. Different meaning.)

A leading Dutch newspaper reported yesterday that scientists have calculated that the two-week pausing of AstraZeneca at the beginning of this month in The Netherlands has probably caused the loss of thirteen lives.

Just to say - if you can seemlessly switch to something else it’s one thing, but remember that not vaccinating costs lives too.

I wonder what the J&J pause did to the US. It didn’t make a huge dent in the supply, but it created a lot of FUD, and seems temporally linked with the decline in Americans being vaccinated. I wonder if that’s a coincidence or if there’s any casual link.

I’m not anti the AZ vaccine - I had my second shot a week ago today, in the midst of this current brouhaha. I did risk-benefit of medicines (some, amongst other things) for a living, so I do get the wider view, and have probably posted to excess on it - see post 354 of this thread for a taster.

My main concern here (and I suspect @eschrodinger’s also) is that, in a rollout of vaccines rushed to market, a rollout thus critically underpinned by pharmacovigilance, the MHRA have done their PV so badly. Months on from this adverse event being identified, they are still struggling to get their pharmacovigilance database in order. It really matters

It would be nice to think that they reached that conclusion on the basis of accurate frequency and demographic data for the adverse event. Do we know if their calculations used the MHRA database? - I guess the UK has had the largest exposure, so that should be the most reliable data source.

See what I’m getting at? For multiple reasons (not least public confidence in vaccination) we need to be making good decisions here. Its tough to do if you don’t have good data to start with.


The later. Demand has scaled back considerably. They are now advertising for walk-in vaccinations. Some states are turning away Vaccine supplies because they don’t have enough demand to warrant it. A month ago I had a heck of a time getting an appointment. Now I’m getting robo-calls, texts and emails on it from various groups including my doctor.

It’s inevitable that we get to the vaccine group who are sitting on the fence. The timing of the J&J pause was about perfect for nudging them to the “no” side of it.

Some real numbers based on national healthcare systems’ ability to find specific events. Denmark and Norway have calculated the rates of blood clots in general and CVST events in correlation with receiving the first shot of the AZ vaccine, and subtracting the background rate.

They found 2.5 CVST cases per 100,000 AZ first shots.

As I’ve mentioned before, I’m not suggesting that people should not get the AZ vaccine, but accurate information is crucial to informed consent, and it should also inform the medical recommendations of doctors as to which vaccine is recommended for which demographic groups.

This rate information will change the risk/benefit ratios that were so quickly produced, which said only very young people in low transmission areas would be better off waiting for a different vaccine. Presumably that equation is different if the CVST rate is more like 1/40,000 than 1/100,000. Particularly if it can be further narrowed down by demographics.

And, of course, as I’ve also previously mentioned, some places have supplies of other vaccines, so that it’s just a matter of allocating that vaccine to those at highest risk from the AZ vaccine, with no one delaying vaccination.

Another good find, @eschrodinger.

For those interested, here’s the BMJ editorial addressing the study. It makes this salient point:

…While subgroup analyses hinted at particularly high risk of thromboembolic events among women younger than 45, lack of a discernible effect in other groups, including men, might be due to the study’s lack of power.

My bold. The excess rate of 2.5 cases per 100,000 vaccinations is an overall figure - some groups appear to be significantly more at risk than others. The suggestion is that a disproportionately high number of the events were seen in young women; with a bigger sample size*, the rate observed in that group may prove to be higher than 2.5 per 100,000; and the rates in other groups lower.

Here’s the study.


* - a bigger sample size will improve a study’s power.