Hannah Kuchler and Clive Cookson © FT montage

People in the UK aged under 30 are to be offered an alternative to the Oxford/AstraZeneca vaccine after a link was found between rare blood clots in the brain and the AstraZeneca shot.

The UK’s medical regulator said people aged 18 to 29 should preferably be offered either the BioNTech/Pfizer or the Moderna jab as an alternative. But what does this mean for those who have already had one dose of the AstraZeneca vaccine? Can you mix vaccines? Why have other countries introduced much tighter restrictions than the UK on the AstraZeneca jab, such as limiting it to over-60s?

Clive Cookson, the FT’s science editor, and Hannah Kuchler, our pharma correspondent, answered your questions about vaccine rollouts across the world throughout the day (GMT) on Friday April 9.

Here are the highlights:

FT Commenter George Smiley: What risk factors have been identified for blood clotting after vaccination with AZ? Smoking? Anything else? Is there any way to guard against clotting before getting an AZ jab? Aspirin?

Clive Cookson: The risk factors are a real mystery. At first it was thought that women were at greater risk than men but subsequent analysis has shown this not to be the case. Our colleague Anna Gross has just written a fascinating article about it. I don’t think taking low-dose aspirin for a few weeks before an AZ jab would do any harm — and it might have a minor protective effect. That’s not something I have heard before.

FT Commenter fabiobeta: How high is the risk of a variant entering the UK and making the vaccine ineffective or of significantly reduced effectiveness? What should we do to minimise that risk, if the risk exists?

Hannah Kuchler: There are concerns that the current vaccines are less effective against the South African strain — but we have no evidence yet that they are completely ineffective. The BioNTech/Pfizer vaccine has shown some early clinical evidence that it remains effective against the strain, J&J and Novavax have clinical studies showing they are less effective but not ineffective. One concerning study showed Oxford/AstraZeneca did not prevent mild or moderate disease caused by the South African variant but it may still protect against more severe disease. 

The more the virus spreads, the more likely variants are to emerge. So the most important factor is limiting the spread of the virus through public health measures and vaccination. Then there are particular issues surrounding protecting the immunocompromised from spreading the disease, as new variants can emerge while they are battling the virus, and around importation from countries where other variants are prevalent. Quarantine, testing and restricting international travel can all have an impact on importing new variants, although as we have seen so far, it isn’t easy. 

FT Commenter FDW: I am interested in your comments on mixing vaccine shots. If the first was AZ then would there be advantages or disadvantages in receiving a second injection with a different two-dose product?

Clive Cookson: There have been several questions about mixing vaccines. Some scientists think there might actually be advantages in training the immune system with different jabs. We’ll soon have more data because France and Germany have decided to give a different second dose to younger people who have received AZ as a first dose.

FT Commenter Paolo Sodini: Why is the EU so slow? What went wrong? Was it an institutional issue, for example competences are unclear and not well assigned between EU and member states? Or just an issue of wrongly designed contracts with the pharma industry? What did the EU miss that the UK and US did not?

Hannah Kuchler: I think this is a question we may be investigating for months — or years — to come. Many point to a difference of approach to the contracting: the US and the UK spent a lot of money funding R&D for vaccines and signed contracts with many vaccine makers, whereas the EU treated it more like a traditional procurement process, mainly buying doses and trying to be tougher negotiating on price, perhaps concerned about not looking like they wasted money or filled the pockets of Big Pharma. The EU signed its deals with the vaccine makers later than the US and the UK and may have secured less advantageous terms. But it is obviously a very complex job to co-ordinate between so many countries. 

FT Commenter David Flaks: Is AstraZeneca’s team working on a potential vaccine modification and/or is there a possibility to counter those blood clot side-effects? If yes, how long could it take? 

Clive Cookson: The problem with countering the blood clotting side-effects is that scientists don’t know what is causing it, beyond the general theory that the vaccine over-activates the immune system. They don’t even know whether the virus spike protein is responsible or the adenovirus vector that AZ uses or some combination of the two. Until the mechanism is known, the AZ team can’t work sensibly on modifications to overcome the problem. 

FT Commenter Sic transit gloria mundi: Why can all US adults have the jab by mid-April whereas the UK is only offering the end of July? Given that the UK has been slightly ahead of the US, this seems like a significant reversal which no one in the UK is talking about. 

Hannah Kuchler: The US has secured large contracts with vaccine makers, most of which make all their vaccine within the country. It will have enough supply to vaccinate every American by the end of May so Biden feels confident about opening up to everyone, whereas the UK has warned it is seeing a drop in supply because of export controls in India and concerns over getting supply from the EU.

It is important to note that when the vaccine is offered by mid-April it means that people in the US can start booking their appointments, it does not mean they will get one immediately. Another factor that may be playing into this is that Americans may be more vaccine-hesitant than the British so the uptake in the currently eligible categories may be lower, though I’ve not seen good data on this yet. 

Do you want to read more questions and answers on the vaccine rollout? The conversation happened in the comments below, so read on.

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