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Comment by seedless-sensat | Hacker News Reader

Except the adverse reaction was not in the US trial.

I followed the first link in the stat article, which says "A large, Phase 3 study testing a Covid-19 vaccine being developed by AstraZeneca and the University of Oxford at dozens of sites across the U.S. has been put on hold due to a suspected serious adverse reaction in a participant in the United Kingdom"

As I read that, it was a UK participant in a AZ and US-run study.

AstraZeneca and Oxford have subjects in the US, UK, Brazil, and South-Africa. The aim was to have diverse make-up of the testing groups, to have an order of magnitude more people in the Phase 3 trial than normal for a vaccine, to test in countries with high infection rates, and to deliver the results on 15th of September. A British subject from the British trial got ill.

I presume these countries have deals with Oxford/AstraZeneca so if a safe vaccine is available, they get guaranteed access. I've heard India is already producing the vaccine ahead of the Phase 3 conclusion. The phase 3 is only on hold since it is not clear if the vaccine was the cause. There are other causes for the adverse reaction, such as viral herpes infection, or onset nerve diseases not caught during subject checkup. Since not all vaccines offer 100% protection (while still being useful), COVID may have also been the cause of spinal nerve inflammation.

As I would classify it, they're running multiple phase 3 trials in multiple countries, but applying policy as if it's one big study (that wasn't clear). An action in the UK study caused all the studies to halt. This is not strictly required, but it's clear they're playing things conservatively.

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