Covid vaccine update: What is the Oxford Vaccine and why is there a 12-week vaccine gap?

We are aware updates are happening all the time and confirm this article was written on 6 January 2021 using evidence-based information available at the time.


Internet searches about the Covid-19 vaccine reached an all-time high last week. With news of the Oxford/AstraZeneca vaccine approval and a divisive 12-week vaccine gap, it comes as no surprise.


We want to save your scrolling. Throughout the pandemic, talkhealth has published up-to-date, accessible and fact-checked vaccine news and we don't intend to stop. This week we cover all things Oxford, rescheduling and roll-out!


On December 30 the Oxford/AstraZeneca vaccine was approved for UK use by the Medicines and Healthcare products Regulatory Agency (MHRA). The thumbs-up came after a rigorous ten months of pre-clinical trials that involved 20,000 volunteers.

Administering this vaccine, and the Pfizer/BioNTech one, is the answer to widespread vaccination in the UK. Especially because the Oxford/AstraZeneca vaccine is made of stronger stuff than its counterpart – it can be stored at lower temperatures; it's easily produced and can be transported easily. Many believe that this vaccine will be our ticket out of lockdown!

The Oxford/AstraZeneca jab is what scientists call an adenovirus-vector vaccine. This vaccine technology has been tried and tested for years and is currently being used in trials for HIV and flu vaccines. The Covid-19 vaccine will be the second adenovirus-vector to treat disease in humans.

Much like the Pfizer/BioNTech vaccine, the jab comes in two doses and is injected into the upper arm.

Both of the vaccines that are available in the UK rely on genetic code that the body reads and reacts to. The difference is: The Oxford/AstraZeneca one uses double-stranded DNA. This is less fragile than the RNA technology used in the Pfizer/BioNTech vaccine.

How does the Oxford/AstraZeneca vaccine work?

Double-stranded DNA of Covid-19 is inserted into a messenger adenovirus. Adenoviruses cause mild common cold symptoms. The scientists at Oxford have taken adenovirus matter from chimpanzees for their vaccine. It can't replicate and cause symptoms once inside a human body.

Once someone is vaccinated with the adenovirus, the body reacts to the Covid-19 DNA strands. The body creates the infamous spike proteins, these are recognised by the immune system which begins to make antibodies and T cells.

The Oxford/AstraZeneca vaccine is also designed to send out warning signals to your immune cells, these warning signals make your immune system react more strongly to the spike proteins.

Your body memorises this immune response if you become infected in the future.

1.3 million people in the UK have received their first dose of a Covid vaccine. The government says that this includes nearly a quarter of the most elderly, vulnerable patients in the country.

The government has pledged to vaccinate everyone in the top four priority groups by the middle of February – that’s 13 million people.

This target can only be met with a change of tac. The 12-week vaccine gap.

Originally, the scientists behind the Pfizer/BioNTech vaccine said that people should receive their second jab within 21 days of their first dose. Last week the MHRA and the Joint Committee on Vaccination and Immunisation (JCVI) advised that 12-weeks should be left between each dose of a Covid-19 vaccine.

Professor Wei Shen Lim, COVID-19 Chair for JCVI, said: ‘For both vaccines, high-levels of protection are evident after the first dose of vaccine. JCVI advises priority should be given to the first dose, to maximise the public health benefits in the current situation and save more lives.’ 

Both vaccine trials have shown that the initial injection provides the most protection against the virus. Two weeks after the first dose the Oxford/AstraZeneca vaccine is 70% effective in fighting off the virus and the Pfizer/BioNTech jab is 90%. 

More people will be receiving the first dose to ensure more widespread protection against coronavirus in the short term. It is still very important that people receive both doses of their vaccination to ensure a prolonged period of protection. 

You can read more about the Oxford/AstraZeneca vaccine here.


Information contained in this Articles page has been written by talkhealth based on available medical evidence. The content however should never be considered a substitute for medical advice. You should always seek medical advice before changing your treatment routine. talkhealth does not endorse any specific products, brands or treatments.

Information written by the talkhealth team

Last revised: 6 January 2021
Next review: 6 January 2024