Now the thrombocytopaenia/ thrombus evidence with ChAdOx is clearer- some thoughts on what this means for populations and individuals

There are 3 questions
1) what should we do at population level?
2) what should we do at individual level?
3) what is best for vaccine confidence?

1) remains simple. We keep vaccinating with whatever we have. Post authorisation vaccine complications were going to be (by definition) rarer that Covid-19 mortality/morbidity.
Every serious analysis concludes this but the figure in the UK that has cut through is the

6000 deaths already prevented. The decision to vaccinate considers not just risks of vaccines but benefits against Covid-19 https://www.bbc.com/news/uk-56521415

This balance was beautifully illustrated in the press conference by the work from the Winton centre https://wintoncentre.maths.cam.ac.uk/news/communicating-potential-benefits-and-harms-astra-zeneca-covid-19-vaccine/

This really is a masterclass in clarity of presentation and hence why it has been shared so widely. It solves a few communication problems. First is that death alone doesn’t get whole picture and so they have chosen ICU admission on Covid-19 side as acomparator to all events

on the vaccine side. I think this is really clever. It captures all the vaccine events and uses a meaningful though different comparator. You could argue it is conservative as many people not admitted to ICU have terrible complications but it is a thing people will understand.

By framing like this we lose additional arguments I will address for personal risk but it is a simple concept, well communicated.

At a population level the evidence is clear. We have limited vaccines. Rare risks will remain a possible issue with all of the vaccines (this will not be the last time we go over in essence the same story) but the specific complications or vaccine under microscope may change.

2) at a personal level we need to accept there is more nuance. The arguments are well rehearsed. Some have nothing to do with your personal risk. If you want societies opened, if you want to cut your risk of infecting friends, family, contacts, if you want to reduce chance

of long term complications (which are common) and if you want to try to avoid the up to 20% of sufferers still off work- these arguments all favour all vaccines.

The thrombocytopenia/thrombosis complication is more convincing now and assuming causality/association

though rare it does mean for personal risk of death/disability from a vaccine we have moved from theoretical (I have always tried to be clear about not being able to rule out rare events until we have vaccinated hundreds of millions) to real risk.

A 25 yr old healthy woman might have a 1 in 300,000 risk of death from Covid-19 and this may be in equipoise with risk of ChAdOx. I think we must be open what the risks are and clear as data allows- personal choice should be respected. However

what we do should be rooted in context. When we have vaccine supplies with choice of vaccines that have all been dosed in 100s of millions with clear real world safety/efficacy then choice will not be vaccine vs Covid-19 but of different vaccines. We are not there right now.

We need to continue to respect individual choice in my opinion and to make as honest a case for vaccination as we can on available data and with conservative assumptions when we don’t have that data.

3) hardest bit. Vaccine confidence is critical here. This is because it is not a simple factor of evidence= confidence. We need to play a long game which may not always mean following the best evidence. Best way to frame this is that we are going back to people later in the year

and asking them to vaccinate again with boosters hopefully in the context of limited disease about. Risk perception therefore will change. We need to make sure we are listening to concerns and building the best long-term strategy for maximising chances of continued high uptake.

This is bigger than any one vaccine and may mean winners and losers for future campaigns based partly on what people will accept. We need to be pragmatic about this. We have a long way to go and have to be careful not to be short-termist about vaccines.