The COVID-19 vaccine developed by the University of Oxford and AstraZeneca is already being administered to the elderly and key workers, with millions more to come in the next few weeks.
Here’s what we know about the Oxford vaccine.
How does the Oxford vaccine work?
The vaccine – called ChAdOx1 nCoV-19 – uses a harmless, weakened version of a common virus which causes a cold in chimpanzees.
Researchers have already used this technology to produce vaccines against a number of pathogens including flu, Zika and Middle East Respiratory Syndrome (MERS).
The virus is genetically modified so that it is impossible for it to grow in humans.
Scientists have transferred the genetic instructions for coronavirus’s specific “spike protein” – which it needs to invade cells – to the vaccine. When the vaccine enters cells inside the body, it uses this genetic code to produce the surface spike protein of the coronavirus.
This induces an immune response, priming the immune system to attack coronavirus if it infects the body.
How effective is the Oxford vaccine?
The Medicines and Healthcare products Regulatory Agency (MHRA) said data showed the vaccine was up to 80 per cent effective when there was a three-month interval between the first and second doses.
Data published by the Oxford team in 2020 showed that when a patient received two standard doses of the vaccine, the efficacy was 62.1 per cent, while those who first received a low dose followed by a standard dose found the vaccine to be 90 per cent effective.
Why does the vaccine need two doses?
While a single dose will provide short-term protection against severe disease, the majority of patients in the Oxford vaccine trial received a second dose within a set frame of time.
The vaccines have been developed this way as it is thought that two doses produce a longer-lasting immune response in the body.
There are other vaccines that require more than one dose. The MMR vaccine for measles, mumps, and rubella, needs two doses. For vaccination against polio, children require five doses in total.
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However, Professor Wei Shen Lim, from the Joint Committee on Vaccination and Immunisation (JCVI), said that people still acquire a high level of protection after a first dose.
He said the JCVI therefore recommends that delivery of an initial dose should be prioritised for both the Pfizer and AstraZeneca vaccines.
Is the Oxford vaccine safe?
Researchers reported their trials do not suggest any significant safety concerns. Regulators, scientists and clinicians have also scrutinised the data.
“As with all vaccines that are approved by the MHRA, this vaccine has demonstrated rigorous safety and quality standards enabling widespread use,” said Dr Gillies O’Bryan-Tear, Chair of policy and communications at the Faculty of Pharmaceutical Medicine.
“Effectiveness and safety monitoring will be continued following use of the vaccine in practice; any person experiencing side effects after receiving the vaccine can report these to the MHRA using the Coronavirus Yellow Card App.”
How many doses of the Oxford vaccine will the UK get?
The UK Government has secured 100 million doses of the Oxford vaccine as part of its contract, enough for most of the population.
The head of the UK Vaccine Taskforce, Kate Bingham, has said she is confident it can be produced at scale and AstraZeneca said it aims to provide millions of doses to the UK in the first quarter of 2021.
How does the Oxford vaccine differ from Pfizer and Moderna’s?
The Oxford vaccine uses a harmless version of a virus that causes the common cold in monkeys, while the jabs from Pfizer and Moderna are messenger RNA (mRNA) vaccines.
An mRNA vaccine uses only the virus’s genetic code, which is injected into the body where it enters cells and tells them to create antigens. No actual virus is needed to create an mRNA vaccine.
These antigens are recognised by the immune system and prepare it to fight coronavirus.
While the Pfizer vaccine must be stored at around -70°C, the Oxford vaccine can be stored at fridge temperature for at least six months. So, it is hoped that the logistics of administering the Oxford vaccine will be relatively straightforward.
Can I have the vaccine if I am pregnant or breastfeeding?
Yes, where the potential benefits are thought to outweigh the risks. The MHRA recommends that people who are pregnant or breastfeeding discuss COVID-19 vaccinations with their doctor.
Can the Oxford vaccine help the elderly?
There have been concerns that a COVID-19 vaccine will not work as well on elderly people, much like the annual flu jab.
Earlier data from the Oxford University and AstraZeneca vaccine trial suggests that there has been “similar” immune responses among younger and older adults.
In a statement earlier this year on its phase two data, Oxford University said its data marked a “key milestone”, with the vaccine inducing strong immune responses in all adult groups.
What does the vaccine do in the body?
The Pfizer, Oxford and Moderna vaccines all provoke an antibody and T-cell response from the body.
Antibodies are proteins that bind to the body’s foreign invaders and tell the immune system it needs to take action. T-cells are a type of white blood cell which hunt down infected cells in the body and destroy them.
Nearly all effective vaccines induce both an antibody and a T-cell response.
A study on the Oxford vaccine found that levels of T-cells peaked 14 days after vaccination, while antibody levels peaked after 28 days.