The experimental vaccine being developed by AstraZeneca and Oxford University against the new coronavirus produced an immune response in early-stage clinical trials, data showed on Monday, preserving hopes it could be in use by the end of the year.
This vaccine, called ChAdOx1 nCoV-19, has been described by the World Health Organization’s chief scientist as the leading candidate in a global race to halt a pandemic that has killed more than 600,000 people. The vaccine prompted no serious side effects and elicited antibody and T-cell immune responses, according to trial results published in The Lancet medical journal, with the strongest response seen in people who received two doses.
How does the vaccine work?
This vaccine 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.
Scientists handle samples from coronavirus vaccine trials at the Oxford Vaccine Group laboratory in Oxford, England, in June (John Cairns/AP)
What are the next steps in the trial?
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.
When will I get a vaccine?
It is possible a coronavirus vaccine will be proven effective before the end of the year, however, it will not be widely available.
Health and care workers will be prioritised as will people who are deemed at high risk from Covid-19 due to their age or medical conditions.
However, widespread vaccination is likely to be, at the earliest, next year even if everything goes to plan.
Read the Full Phase 1/2 trial results as published by Lancet HERE