ITV Science Editor Tom Clarke answers the key questions about the AstraZeneca vaccine. You can watch above or listen to it as a podcast below
The Oxford/AstraZeneca vaccine will be withheld from anyone under 30 so experts can investigate whether the jab is linked to rare brain blood clots or not.
Some European countries have restricted the vaccine use in younger people following reports of cerebral venous sinus thrombosis (CVST) – a specific type of clot that prevents blood from draining from the brain, as well as low platelet counts – cells that help blood clot.
On Tuesday, it was announced that the trial of the Oxford/AstraZeneca vaccine in children has been paused while UK regulator the Medicines and Healthcare products Regulatory Agency (MHRA) investigates the CVST reports.
Here's what Wednesday's developments mean for the vaccine rollout:
What has been announced?
The Oxford/AstraZeneca vaccine will, for the time being, not be given to anyone under 30 in the UK while experts further investigate potential links between the vaccine and cases of blood clots.
Cases have been extremely rare – and scientists insist the benefits of the jab far outweigh the risks – but regulators say this is a precautionary move to be certain of potential link, if any exists.
Video report by ITV Science Editor Tom Clarke
How many blood clots have been reported?
There have been 79 cases and 19 deaths out of around 20 million AstraZeneca jabs across the UK and the EU.
This equates to almost four cases in every one million doses, and an average of one death per million vaccines.
I'm under 30 - what jab will I be given if I can't have AstraZeneca?
The Pfizer/BioNTech vaccine is still being rolled out and the UK has ordered 40 million doses in total – enough to fully vaccinate nearly one-third of the UK population.
Moderna’s jab is the only other to also be cleared for use in the UK, with 17 million doses ordered in all. This vaccine is already being used in Scotland and Wales and is expected to be rolled out in England in the third week of April.
These vaccines have been ordered but await approval for use in the UK:
Novavax – there are 60 million doses ordered and approval could be confirmed in April. The jab is being manufactured in Barnard Castle.
Johnson & Johnson - with 30 million doses ordered, this jab could be crucial in speeding up the rollout because it only requires one injection. The vaccine has been approved for use in the US but awaits the green light in the UK.
Valneva – Another 60 million doses are expected in the UK, and the jab is to be made in Livingston, Scotland. Early results have been encouraging as the vaccine begins phase 3 trials, which is the final stage.
I'm in my early 30s, should I still accept the jab when I'm offered it?
Anyone who is aged in their early 30s and in good health should still get the coronavirus jab as "the balance is in favour of being vaccinated because of the risks of Covid-19 and the protections the vaccine offers," Professor Wei Shen, chair of the Joint Committee on Vaccination and Immunisations (JCVI) said at a briefing on Wednesday.
Anyone with concerns should look at the available data and information and "make their own decision about what they want to do about vaccination", he added.
I'm under 30 and I've already had the Oxford/AstraZeneca jab - shall I have the second dose?
All 79 cases of the rare blood clotting syndrome were detected between four and 28 days after the first dose of the jab. Therefore, if you've had your first dose and not had any serious side effects, it's extremely unlikely you'll develop it after receiving your second dose.
How do I know if I have a blood clot?
Symptoms include a severe headache, which is tricky because many people do report getting a headache after a jab.
But if the headache persists for more than four days and it is severe, then that could be a symptom.
Swelling in the legs is another one, difficulty breathing and chest pains as well. Pin pricks on the surface of the skin – a kind of bruising – that’s not near the part of your arm where you had your injection has also been listed as another symptom.
It’s important to stress these cases are extremely rare (just four in every million), but if you do have any concerns after your injection you should consult your GP.
If you have a history of blood clots, then the advice is not to take the vaccine but if you have already had the first dose then you should check with a specialist first.
Will this delay the UK's vaccination programme?
Given the pause applies only to those under 30, there is still some time before the affected age groups begin vaccinations en masse.
In England, the government aims to finish inoculating the nine priority groups by April 15, while over-50s are being invited to book appointments themselves across the UK.
Over-40s and over-30s will be next in line before under-30s are given the jab.
People aged 20-29 could expect their turn to come around possibly after the middle of June, by which point the UK’s vaccine supply could be complemented by other jabs such as Moderna and Johnson & Johnson.
However, England’s deputy chief medical officer Professor Jonathan Van-Tam acknowledged the change in recommended use of the AstraZeneca vaccine might result in delays and longer journeys to receive the jab.
He told a press conference on Wednesday: “The NHS has a message that we will get the right vaccine to you in the right time according to the new JCVI advice.
“There might be a small delay sometimes, there might be a slightly greater distance that some people might be asked to travel.
“But the NHS is all over this and understands the challenge of making the advice from JCVI truly operational in a smooth way.”
Listen to our coronavirus podcast:
I'm over 30 and had the AstraZeneca jab - should I be worried by this announcement?
No. Scientists believe any risk becomes greater in younger age groups.
It’s also important to note that the younger you are, the lower your risk of dying from Covid – so the risk of the vaccine (if there is any) becomes more significant.
Government scientific adviser, Professor Calum Semple, has said he is “not worried one little bit” about headlines around the AstraZeneca vaccine.
Speaking in a personal capacity, the Sage scientist told LBC radio: “I’ll take myself, I’m 53, my risk of death from Covid is about one in 13,000, for me it’s a no-brainer, I need to have the vaccine.”
He later added: “This vaccine is safe. What do I mean by safe? You can look right, look left, look right again cross a road, it’s safe to cross because you don’t see any cars (but) you can trip, you can stumble.
“Nothing is risk-free, but is the vaccine safe? I would say yes.”
Have blood clots been linked to the Pfizer vaccine as well?
No – and this is what has caused some concern when it comes to the AstraZeneca vaccine.
Professor Adam Finn, a member of the government’s Joint Committee on Vaccination and Immunisation, said on BBC Newsnight: “I think personally it’s surprising that we haven’t seen any cases with Pfizer if it’s simply uncausal.
“So that’s one of the reasons we’re concerned about this.”
Will aspirin reduce risk of blood clot?
It’s unlikely, but it's best to check with your GP first if you are considering taking aspirin.
The development of these particular blood clots that may be linked to the vaccine is different to that of normal blood clots.
In other words, these blood clots are not caused because of platelets in the blood, so it is unlikely blood-thinning drugs would help.
Are risks normal?
Most medicines and treatments do have side effects.
Take chemotherapy, for example. There are some potentially severe side-effects to the treatment but the benefits are also huge.
Even everyday pills like paracetamol come with warnings and the oestrogen in the contraceptive pill – widely hailed as key to preventing unplanned pregnancy – may cause your blood to clot more readily.
But what it all comes down to is the balance between the benefits and risks, and in AstraZeneca’s case the experts still encourage everyone eligible to take their shot.
We should also consider that, given that we normally don't distribute vaccines at this kind of speed and volume, you could have a side-effect like this in other jabs for other diseases - but because it is so rare it wouldn’t even register.
We shouldn’t be surprised and this is not a sign that any corners have been cut – the vaccine is still safe and effective.
Professor Van-Tam used a nautical analogy to describe the “course correction” in the vaccination programme.
He said it was “quite normal” and “business as usual” for medics to alter their preferences on how to treat patients.
“This is a massive beast that we are driving along at enormous pace with enormous success, this vaccine programme,” he said.
“If you sail a massive liner across the Atlantic then it’s not really reasonable that you aren’t going to have to make at least one course correction during that voyage.”
What has the European Medicines Agency (EMA) said?
The EU medicines regulator has ruled that blood clots are a "very rare" side effect of the AstraZeneca/Oxford Covid-19 vaccine and the benefits outweigh the risks.
Giving an update on Wednesday, Emer Cooke, executive director of the European Medicines Agency (EMA), said its review “confirmed that the benefits of the AstraZeneca vaccine in preventing Covid-19 overall outweigh the risk of side effects,” adding: “Vaccination is extremely important in helping us in the fight against Covid-19.”
Amid fresh concerns over whether the jab could cause blood clots, the EMA said it could not conclude whether there were increased risks of rare blood clots in younger people.
It said most of the cases of blood clots reported have occurred in women under 60 within two weeks of vaccination, but "because of the different ways the vaccine is used in different countries", it could not conclude on specific risk factors.