UK has authorized AZ/Oxford vaccine.

Importantly: UK is leading the way in taking a bold public health approach (vs individual health) to getting the population vaccinated - Prioritizing distribution of 1 dose & delaying dose 2 up to 12 weeks.

1/x https://www.bbc.com/news/health-55280671

This bold move is going to cause ppl to scrutinize the decision. But in this pandemic, too few governments have acted swiftly to limit spread - bc quick action sometimes means imperfect data.

Here, robust data isn’t likely available for a 12 week delay for dose 2

But...

2/x

This was a good decision that

a) need not be permanent and suggests the UKG is willing to think with agility here and

b) likely will be the better overall public health approach rather than letting doses sit in freezers while others die and

3/x

And

c) this experience in next 2-3 months will provide crucial information for the UK and the world that has the potential to provide massive benefits in terms of (i) speed to achieve herd immunity across populations and (ii) get entire extra countries vaccinated in 2021.

4/x

I commend the UK Gov for taking a bold step toward recognizing the gravity of the problem, weighing the available data against the potential benefits and making a decision grounded in optimizing public public gains over individual health gains. The distinction is crucial.

5/5

Could the program backfire? Maybe. Is it likely to? No.

The boosters will be given by 12 wks. For this to be worse than letting doses sit in freezers, the vaccine would have to essentially lose all benefits during months 2 and 3 and ability to boost at 8-12 weeks. Very unlikely

Regarding efficacy concerns

Say, you take pop that received single dose, and ask “how bad would efficacy need to be to be worse than alternative”

If alternative 2 dose regimen is 90% efficacy, then pop eff would be 45% (50% vaccinated).

So, months 2/3 post dose 1 must be >45%

If we convert public health thinking in this case into a closer to home medical dilemma, this is sort of the question faced when making this decision of spacing the vaccines to 12 weeks instead of 4 given imperfect data https://twitter.com/michaelmina_lab/status/1344209676968325120

With @zeynep we wrote about the need to think critically about these questions of single dose vs two dose vaccines to optimize public health effectiveness, particularly given how good the (very limited) signal after single dose of mRNA vaccines https://www.nytimes.com/2020/12/18/opinion/coronavirus-vaccine-doses.html

And here is data for a single dose AZ vaccine which looks essentially as good as two doses through 150 days.

Further supporting this decision. https://twitter.com/nickhassey/status/1344190327222136832