A Covid vaccine from Oxford University and the pharmaceutical company AstraZeneca is being considered for use in the UK.
It follows the roll-out of the Pfizer vaccine, which was the first to be approved.
What is the Oxford vaccine and how does it work?
It is made from a weakened version of a common cold virus (known as an adenovirus) from chimpanzees. It has been modified to look more like coronavirus – although it can’t cause illness.
When the vaccine is injected into a patient, it prompts the immune system to start making antibodies and primes it to attack any coronavirus infection.
The UK has ordered 100 million doses. Unlike Pfizer’s jab – which has to be kept at an extremely cold temperature (-70C) – the Oxford vaccine can be stored in a normal fridge. This makes it much easier to distribute.
How has the vaccine been produced so quickly?
That meant a lot of the building blocks were already in place, and scientists weren’t starting from scratch.
The vaccine has been through all the usual research stages, although for speed these have overlapped when they would usually happen one after another.
And the UK’s medicines regulator – the MHRA – has been carrying out a “rolling review” of data all year.
When will the vaccine be ready?
Prof Sarah Gilbert, lead researcher on the vaccine, has said the chances it will be given to people before the end of the year are “pretty high”.
How effective is the Oxford vaccine?
The Oxford/AstraZeneca vaccine has been shown to be safe and to provoke an immune response in people of all ages, including the over-55s.
Overall, the vaccine was found to be 70% effective.
For the majority of people in the trial who got two full doses the figure was 62%.
However, for a small group who got a half dose and then a full dose, that figure was 90%. It’s not clear yet why the results were better for this group.
It may be that their immune systems were primed more gradually, but the scientists can’t yet explain it.
Also, all the volunteers in this smaller group were under 55.
And as with the other vaccines, scientists don’t yet know if it stops people catching Covid – that’s something they won’t know until they can see the impact of vaccination over time.
Which dose will be recommended?
That is something the MHRA will consider.
It will keep analysing data from the ongoing Oxford/AstraZeneca research, so it could opt for two full doses initially – but rule on the half/full course once more data is available.
Is the Oxford vaccine as good as the Pfizer?
It’s important to remember even the lower 62% figure is a better result than the best flu jab, which is about 50% effective.
And no-one who got the vaccine was hospitalised or got seriously ill due to Covid.
How long does it protect against Covid for?
As with all the vaccines being developed against coronavirus, we don’t know yet.
It may be that people need annual vaccinations, as happens with the flu jab.
Which vaccine will I get?
Recommendations on which vaccine is given to which groups are made by the JCVI – the Joint Committee on Vaccination and Immunology – an independent group of scientists.
It was the JCVI that decided the Pfizer vaccine should first go to over-80s, health and care workers and care home residents.