The University of Oxford COVID-19 vaccine explained
How does the Oxford COVID-19 vaccine work?
The Oxford COVID-19 vaccine has been developed using a method which was previously used to create a vaccine for another coronavirus, Middle East Respiratory Syndrome (MERS). The vaccine was shown to induce a strong immune response, meaning it would be likely to create immunity in those who received it. The MERS Oxford vaccine has not yet completed the clinical trials stage due to falling infection rates.
Like previous vaccines produced by the same institute, the ChAdOx1 nCoV-19 vaccine from the University of Oxford is made using a modified version of an adenovirus, a chimpanzee virus that usually causes the symptoms of a common cold. The adenovirus has been manipulated so that it is harmless to humans and cannot reproduce within the body, and also holds the genetic instructions to teach the body how to create coronavirus antibodies. The vaccine induces an immune response which creates the necessary antibodies that the body needs to fight coronavirus, creating immunity in the patients who receive it.
How was the Oxford vaccine developed?
Every vaccine must go through a number of different stages in development, usually starting with the exploratory stage, before moving on to the pre-clinical stage, which involves testing the vaccine either in a laboratory or on animals. Once the vaccine is determined to be safe to test on humans, and has a good chance of creating immunity, it can then be tested on humans.
In the case of the Oxford COVID-19 vaccine, after preliminary testing on animals, development went into to the human trials stage. Additional pre-clinical testing is being conducted in parallel with clinical trials.
Animal testing results
In addition to the vaccine being tested on groups of volunteers, tests have been made on rhesus macaques, which are considered to have a similar immune response to humans. The findings (which have not yet been peer-reviewed) showed that after being given one dose of the vaccine, this “significantly reduced viral load” in the monkeys, and they were protected from contracting coronavirus-related pneumonia in the lungs. However, they also still had just as much coronavirus genetic material in their noses as unvaccinated monkeys, meaning that all of the vaccinated and unvaccinated monkeys were infected with COVID-19.
This could be for a number of reasons. It has been suggested by Dr Sarah Gilbert, one of the lead researchers developing the vaccine, that the high levels of coronavirus molecules present in the noses of the monkeys could be due to the fact that they received very high doses of the virus. It is also unclear as to whether the virus particles found in the noses of the monkeys were actively infectious, as they could also be “inactivated” byproducts of the body’s immune response.
Alternatively, it has been suggested that the vaccine can only produce immunity in the lungs, but not in the mucous membranes in the nose. According to some immunology experts, this has been the case with previous coronavirus vaccines.
Human trial stage
Clinical trials are usually made up of three different phases. In phase I, small groups of volunteers receive the vaccine to ensure it is safe. In phase II, the effectiveness of the vaccine is determined with a larger group of volunteers. In phase III, an even larger group of volunteers receives the vaccine, which tests the effectiveness and safety of the vaccine on a diverse group of people of different ages and backgrounds. This ensures that the vaccine will work for everyone.
The Oxford COVID-19 vaccine was one of the first in the world to begin testing on groups of volunteers. Starting in April 2020, combined phase I and II testing began when more than 1,000 volunteers received the experimental vaccine in the UK. Falling levels of coronavirus infection meant that phase II/III of clinical trials were then conducted in other countries.
Trials for the Oxford vaccine have taken place in the UK, Brazil, South Africa, Japan, and Kenya.
When will the Oxford vaccine be ready?
AstraZeneca, the biopharmaceutical company working with scientists at Oxford University to produce the vaccine, began manufacturing doses of the vaccine during the summer of 2020. AstraZeneca committed to delivering 400 million doses of the vaccine by the end of 2020, ready for distribution once the vaccine had completed clinical trials and has been given regulatory approval.
The Oxford vaccine was given regulatory approval by the Medicines and Healthcare products Regulatory Agency (MHRA) on December 30, 2020.
The first shots were administered on January 4, 2021.
How effective is the Oxford vaccine?
Analysis from the clinical trials of the vaccine suggest that it could be up to 90% effective, however, the trial that produced this result (in which volunteers were given a low dose followed by a high dose) only included people under the age of 55.
The overall result of the initial clinical trials is that the vaccine is 70.4% effective.
The vaccine has subsequently been shown to have varying levels of effectiveness against different variants of coronavirus.
Does the Oxford vaccine have side effects?
Vaccines work by stimulating an immune response so that the body learns how to fight coronavirus. After receiving the vaccine, many people experience some of the same bodily responses that they might after catching an infection.
Find out more about the side effects of coronavirus vaccines.