Have you looked seriously into the blood clot question? I may have missed a more detailed account of your position, but my perception over the past several months has been that you’re conflating ‘this is not worth worrying about in the present context’ with ‘this is not a real effect’, and that you may have justified grounds for the first claim and not for the second.
The distinction is relevant to me, an Australian who has to choose between AZ now and Pfizer soon, and whose current risk of catching Covid is extremely low. TTS is just one consideration among many, and perhaps it is swamped by the others, but I don’t think that’s obvious enough to skip the step of estimating the risk and taking it into account.
The Australian authorities appear to have good grounds for considering the TTS risk from AZ to be significantly above baseline. If the risk from Pfizer is similarly elevated then it probably becomes irrelevant, but it’s not clear to me that the study you linked establishes that or even provides good evidence for it. See this comment on the linked page:
This is an important study, however there are some key questions remaining. The syndrome known as vaccine-induced thrombocytopenia and thrombosis (VITT) or thrombocytopenia and thrombosis syndrome (TTS), so far attributed to ChAdOx1 vaccination, is not a general clotting and thrombocytopenia condition, but a specific immune reaction mediated by anti platelet factor 4 (PF4) auto antibodies. In Australia we have been monitoring development of this condition very closely and, so far, we have detected cases of VITT following vaccination with ChAdOx1 only and not with BNT162b2. Please note that VITT is a specific syndrome with thrombosis occurring in uncommon places (eg brain venous sinuses, splanchnic veins) and high levels of markers such as D-dimer. Since this is still a rare reaction (various estimates, but about 3 per 100,000 doses), it’s likely that population-based studies are not able to detect these small increases (especially since other types of thrombocytopenia and thrombosis, unrelated to VITT, are also present). The reason for concern about VITT was its high mortality rate when it was first identified. Now that the syndrome is understood in more detail, treatment options are available and the mortality rate has decreased significantly. Whether this type of autoimmune reaction occurs with BNT162b2 is yet to be determined.
(From what I have read, I believe that the non-fatal outcomes are often quite serious. So a relatively low mortality rate, while obviously welcome, is not the whole story.)
Very much agree with this—we have adverse event data from tens of millions of vaccinations, so it seems odd to suddenly ignore that on the basis of this study (doesn’t look at deaths as far as I can see, and only looks at ~400,000 AZ vaccinations, mostly in people aged over 60).
My understanding is that the larger point, apart from any comparison between the AZ and Pfizer vaccines, is the “blood clot question” seemed to ignore the general population baseline. I interpreted Zvi’s point about the new study as being evidence that there’s no extra risk from the vaccines above the baseline risk.
It would also require our authorities to be complete idiots, beyond the level of incompetence one could reasonably expect. Unless it has literally been paid off by Pfizer, the Australian government does not have an interest in spreading FUD about AZ; quite the opposite, because our vaccine rollout strategy relied quite heavily on AZ and has been impacted in a politically-damaging way by TTS fears.
(Please note that I’m definitely not trying to discourage anyone from getting the vaccine; it is clearly much much better than taking one’s chances with Covid. The practical relevance of this debate is specific to my situation as a cautious hermit in a place with very low prevalence and other vaccines expected to be available soon.)
Have you looked seriously into the blood clot question? I may have missed a more detailed account of your position, but my perception over the past several months has been that you’re conflating ‘this is not worth worrying about in the present context’ with ‘this is not a real effect’, and that you may have justified grounds for the first claim and not for the second.
The distinction is relevant to me, an Australian who has to choose between AZ now and Pfizer soon, and whose current risk of catching Covid is extremely low. TTS is just one consideration among many, and perhaps it is swamped by the others, but I don’t think that’s obvious enough to skip the step of estimating the risk and taking it into account.
The Australian authorities appear to have good grounds for considering the TTS risk from AZ to be significantly above baseline. If the risk from Pfizer is similarly elevated then it probably becomes irrelevant, but it’s not clear to me that the study you linked establishes that or even provides good evidence for it. See this comment on the linked page:
(From what I have read, I believe that the non-fatal outcomes are often quite serious. So a relatively low mortality rate, while obviously welcome, is not the whole story.)
Very much agree with this—we have adverse event data from tens of millions of vaccinations, so it seems odd to suddenly ignore that on the basis of this study (doesn’t look at deaths as far as I can see, and only looks at ~400,000 AZ vaccinations, mostly in people aged over 60).
My understanding is that the larger point, apart from any comparison between the AZ and Pfizer vaccines, is the “blood clot question” seemed to ignore the general population baseline. I interpreted Zvi’s point about the new study as being evidence that there’s no extra risk from the vaccines above the baseline risk.
That explanation is incompatible with the finding that TTS is an order of magnitude less common after the second dose than after the first. (see e.g. https://mvec.mcri.edu.au/references/thrombosis-with-thrombocytopenia-syndrome/)
It would also require our authorities to be complete idiots, beyond the level of incompetence one could reasonably expect. Unless it has literally been paid off by Pfizer, the Australian government does not have an interest in spreading FUD about AZ; quite the opposite, because our vaccine rollout strategy relied quite heavily on AZ and has been impacted in a politically-damaging way by TTS fears.
edit: better links are https://www.tga.gov.au/periodic/covid-19-vaccine-weekly-safety-report-05-08-2021 and https://www.health.gov.au/news/atagi-update-following-weekly-covid-19-meeting-28-july-2021 .
(Please note that I’m definitely not trying to discourage anyone from getting the vaccine; it is clearly much much better than taking one’s chances with Covid. The practical relevance of this debate is specific to my situation as a cautious hermit in a place with very low prevalence and other vaccines expected to be available soon.)