This issue is, appropriately, contentious. As a vaccinologist - & citizen & relative of people in at-risk groups - I fully support the UK decision to increase dose intervals of both our Ox/AZ product and the Pfizer product. I'd happily receive either with a >8w gap. Here's why 🧵

For the Ox/AZ vaccine, it's fairly simple. The trial demonstrated efficacy at a range of dose intervals. Antibody responses after the boost were significantly stronger with longer intervals - see table 3.
https://t.co/10KPvahJ64
(so in response to @drmarkporter's point, higher immune responses with a longer interval is proven & now public. I haven't seen a similar analysis for efficacy against disease but the data exists and I suspect the regulators & JCVI committee have)
For Pfizer, there isn't direct evidence of efficacy with a >3wk interval. But as widely publicised, efficacy in the period from 14 days after first dose to 21 days is high.
Can we extrapolate from this to a longer interval? It's a judgment call. On one hand is evidence-based medicine's scepticism of anything not directly proven 'beyond reasonable doubt' in an RCT; on the other is a 'balance of probabilities' approach based upon the biology.
Based upon the biology, I'd eat my hat if the Pfizer vaccine is substantially less effective with a longer dose interval. Most vaccines induce stronger immune responses with longer intervals. A couple of examples below. There are more.
Regimes like the Ox/AZ use the same adenoviral vector to prime & boost so face 'anti-vector immunity' (immunity from the first dose to the viral 'postman' which must delivers the spike protein 'message' for the boost). This favours longer intervals specifically for Ad/Ad but...
...the above shows that longer intervals are better for regimes with different viral vectors, DNA priming, inactivated virus boosting - this isn't just an adeno effect. It's v rare for a 3wk interval to give stronger responses than 8+ wks (I can't think of examples, can you?)
Mechanistically, at 3w, the immune response to prime isn't complete- it hasn't yet produced all the memory B cells which give the best response to the boost. Once they are made, the memory cells last years! They won't forget how to respond to a boost in a few months.
I appreciate mechanistic arguments often prove to be wrong, and RCT evidence with Pfizer at longer intervals should definitely be produced ASAP... but as @zeynep has written in an excellent article today:
https://t.co/WrNVW5jRaW
There is a good debate:
@Bob_Wachter has written thoughtfully https://t.co/wZgvN937DV

@trishgreenhalgh @EricTopol @nataliexdean have all argued the other way from me - would welcome their thoughts on the above 🧵
I haven't yet seen a vaccine immunologist who has personally done experiments giving vaccines at different intervals and who is concerned about the longer interval... but I look forward to hearing that view too...

More from Government

Oh my Goodness!!!

I might have a panic attack due to excitement!!

Read this thread to the end...I just had an epiphany and my mind is blown. Actually, more than blown. More like OBLITERATED! This is the thing! This is the thing that will blow the entire thing out of the water!


Has this man been concealing his true identity?

Is this man a supposed 'dead' Seal Team Six soldier?

Witness protection to be kept safe until the right moment when all will be revealed?!

Who ELSE is alive that may have faked their death/gone into witness protection?


Were "golden tickets" inside the envelopes??


Are these "golden tickets" going to lead to their ultimate undoing?

Review crumbs on the board re: 'gold'.


#SEALTeam6 Trump re-tweeted this.

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