Thought a longer thread on the Pfizer delayed dose in UK might be useful. 1/n
Firstly important to keep local UK context clear. Pfizer will end up a minority vaccine in UK so this will not have much of a long-term effect on population coverage. However because of the way we are prioritising, it will disproportionately land in 2 groups. 2/n 
Those are HCWs and over 80s. HCWs are as a population low risk for serious complications. They are at the front of the queue for the same reason you put your O2 mask on yourself first before your child on an airplane. Right now we are generally pretty critical. 3/n
We already have high staff loss/sickness and vaccine coverage ensures we can keep the show on the road. You could argue this for those involved in food chain, teachers, refuse collectors, petrol station workers etc etc (you get the point). So we are taking a low risk group... 4/n
...who nonetheless have very high rates of disease and are critical to national response and prioritising them. If public get sick we will still be there at bedside. Seems reasonable but a choice and not inevitable. So having agreed on this I personally am happy... n/5
... to basically "give' my second dose away and have it later. Someone else gets covered and might save some lives. I am willing to bet most in the over 80s group feel the same but would be interesting to hear on threads. This position is not irreversible and if data... n/6
...emerges in the coming weeks that shows we are seriously impacting on vaccine efficacy then we can change direction. There are plenty of centres out there competing to be the first to publish this data. The large ChAdOx trial has 10k+ still enrolled and the control... n/7
... population mostly switched to Pfizer because it was the first licensed. Subjects continue to have visits so data will be coming out in real time. You will get data on this. n/8
So we might impact slightly on rates of disease and transmission, or we might increase coverage and save lives. Those are the choices. Neither have evidence on a population scale. It is easy to point out we are deviating from "evidence basis" but I would say we should view... 9/n
...this from population perspective. 50% doses in midst of worst wave vs 100% but possibly poorer protection. What saves more lives? Truth is we don't know. And the current wave is the real world context. You can't get away from it. If we were in a trough right now... 10/n
..my opinion might be different (spoiler alert it probably wouldn't) but we aren't. So on balance I am supportive of this calculated gamble. I think real time data needs to be collected and we change tack if it looks like it isn't working. I think we need to remember this... 11/n
..is not the major vaccine we are dosing with and that further down the line I will be amazed if we aren't having to have vaccine mark 2.0 when the first variant to demonstrate resistance emerges so it is not the end of your personal vaccine story. Last thing... 12/n
...at some point we need to start talking about "repertoire freeze"!
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