How does the vaccine work?
How does the vaccine work?
The vaccine – called ChAdOx1 nCoV-19 – is being developed at unprecedented speed.
It is made from a genetically engineered virus that causes the common cold in chimpanzees.
It has been heavily modified, first so it cannot cause infections in people and also to make it “look” more like coronavirus.
Scientists did this by transferring the genetic instructions for the coronavirus’s “spike protein” – the crucial tool it uses to invade our cells – to the vaccine they were developing.
This means the vaccine resembles the coronavirus and the immune system can learn how to attack it.
What are antibodies and T-cells?
Much of the focus on coronavirus so far has been about antibodies, but these are only one part of our immune defence.
Antibodies are small proteins made by the immune system that stick onto the surface of viruses.
Neutralising antibodies can disable the coronavirus.
T-cells, a type of white blood cell, help co-ordinate the immune system and are able to spot which of the body’s cells have been infected and destroy them.
Nearly all effective vaccines induce both an antibody and a T-cell response.
Levels of T-cells peaked 14 days after vaccination and antibody levels peaked after 28 days. The study has not run for long enough to understand how long they may last, the study in the Lancet showed.
Prof Andrew Pollard, from the Oxford research group told the BBC: “We’re really pleased with the results published today as we’re seeing both neutralising antibodies and T-cells.
“They’re extremely promising and we believe the type of response that may be associated with protection.
“But the key question everyone wants to know is does the vaccine work, does it offer protection… and we’re in a waiting game.”
The study showed 90% of people developed neutralising antibodies after one dose. Only ten people were given two doses and all of them produced neutralising antibodies.
“We don’t know the level needed for protection, but we can maximise responses with a second dose,” Prof Pollard told the BBC.
Is it safe?
Yes, but there are side-effects.
There were no dangerous side-effects from taking the vaccine, however, 70% of people on the trial developed either fever or headache.
The researchers say this could be managed with paracetamol.
Prof Sarah Gilbert, from the University of Oxford, UK, says: “There is still much work to be done before we can confirm if our vaccine will help manage the Covid-19 pandemic, but these early results hold promise.”
What are the next steps in the trial?
The results so far are promising, but their main purpose is to ensure the vaccine is safe enough to give to people.
The study cannot show whether the vaccine can either prevent people from becoming ill or even lessen their symptoms of Covid-19.
More than 10,000 people will take part in the next stage of the trials in the UK.
However, the trial has also been expanded to other countries because levels of coronavirus are low in the UK, making it hard to know if the vaccine is effective.
There will be a large trial involving 30,000 people in the US as well 2,000 in South Africa and 5,000 in Brazil.
There are also calls to perform “challenge trials” in which vaccinated people are deliberately infected with coronavirus. However, there are ethical concerns due to a lack of treatments.