The AZ Vaccine And The Rare But Serious Clotting Disorder.

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Update IV, Sat April 10th: The paper, mentioned as a pre-print in the original post, from the German group that originally described the issue has now been peer-reviewed and published in the New England Journal of Medicine...Here....A companion paper that comes, essentially, to the same conclusions from a Norwegian group is...Here.

Update III, Wed April 7th...The European Medicines Agency has provided an update, supported by data from the UK and concludes that this is a rare adverse event...We discuss this update...Here.

Update II, Wed Mar 31st...BC is now offering AZ Vaccine to folks 55-65 in the Lower Mainland due to the high rates of viral infection in the region...Announcement is here....Pharmacies to contact are here...I'm in the age group and will be getting the vaccine...The syndrome described below is  very rare and there is now a protocol to treat it if it does occur.

Update I, Tues March 30th, at bottom of post

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On Saturday March 27th the top of the ladder journal Science published an information piece (i.e. not a primary data paper) on the rare but serious cases of blood clotting/thromboses with platelet problems in folks who have received the AstraZeneca COVID-19 vaccine. 

The piece was written by contributors Kai Kupferschmidt and Gretchen Vogel and it is good.

One of the issues is the differing incidence rates in various jurisdictions including...

The UK:

...The United Kingdom has officially reported only 5 cases—despite administering 11 million doses of the AstraZeneca vaccine...

Compared to, for example, Norway:

...Norway, which has administered the AstraZeneca vaccine to 130,000 people under 65, has reported five patients who had low platelets, hemorrhage, and widespread thromboses, three of whom died...


Why the difference?

Well, one possible explanation is the way the vaccine was initially used in continental Europe compared to the UK:

...So far, most cases have been observed in women under 65. But that could be because of the vaccinated population: Many countries initially used AstraZeneca only in people under 65 because early clinical trials included few older recipients. That meant the vaccine was used in priority groups such as health care workers and teachers, a majority of whom are women. In Norway, for example, 78% of the AstraZeneca doses went to women, says Sara Viksmoen Watle, chief physician at the Norway Institute of Public Health. The United Kingdom, however, used the vaccine first in older people, which may explain why fewer unusual clotting events have been spotted there...


So, can this problem be dealt with?

Well, there is a group in Germany led by a researcher named Andreas Greinacher that is calling the syndrome 'vaccine-induced prothrombotic immune thrombocytopenia' (VPIT). They think that VIPIT has similarities to another rare condition called 'heparin-induced thrmobmocytopenia' (HIT) that is caused when the body makes its own antibodies against a complex of the blood thinner heparin and a factor called PF4  that causes massive platelet activation and thus clotting. Greinacher says that VPIT can be diagnosed and treated in a manner similar to the way that HIT is dealt with:

...Greinacher agrees on the need for more data. But he says it's crucial to alert doctors to the potential complication. When recognized in time, HIT can be treated with immunoglobulins—nonspecific antibodies from blood donors—that help put the brakes on platelet activation. Non-heparin blood thinners can help dissolve the clots. VIPIT should be treated in a similar way, he says. In at least one case, Greinacher says, a doctor sought the group’s advice and the patient recovered...


The work of the German group has not yet been peer-reviewed, but they have placed the data on a public pre-print server so that it can be scrutinized by experts in the field. And, at the very least, the British Society for Hematology and the German Society for the Study of Thombosis and Hemostasis (of which Dr. Greinarcher is a member) are taking the matter very seriously and issuing guidelines for monitoring and potentially treating the issue. In addition, the European Medicines Agency is having a very close look at all the data and it is expected to report on the matter next week (Apr 6-9th). 

Given all this a number of jurisdictions have put age restrictions on the AZ vaccine:

...Many countries are, for now, accepting the risk that the AstraZeneca may carry, but several have restricted its use to people who are at the highest risk of dying from COVID-19: those aged 55 or older in France, 65 or older in Sweden and Finland, and 70 or older in Iceland...


It would appear that Canada's decision to do the same, despite the fact that no cases this disorder have yet been detected after the administration of 300,000 doses of the AZ vaccine nationally, is, at least for the moment, a prudent one, particularly given that we have other vaccines at hand.

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The National Advisory Committee on Immunization (NACI) recommendation and rationale is...Here.

The Ontario Science Table's COVID-19 Response website also has an excellent primer on VPIT....Here.

Apologies for being mostly offline as this and the variant growth has been unfolding locally but it's grant writing season for me which has curtailed my reading on all things COVID somewhat for the last couple of weeks or so.

Update, Tues Mar 30th: Kai Kupferschmidt, one of the co-authors of the piece quoted above, reports on Germany's updated numbers... 2.7 million AZ vaccine doses administered, 31 cases of cerebral venous thromboses (29 in women age 20-63), 19 with thrombocytopenia...This is likely a considerably higher rate than would be seen in the population.

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