The vaccine developed and tested by a team at the University of Oxford is one of the most promising of the many candidates developed around the world to protect against Covid-19. Australia has now signed a letter of intent with pharmaceutical company AstraZeneca to deliver the vaccine to Australians if it allows for safety and efficacy trials, with the PM now saying it won’t be mandatory but will will be encouraged.
Here’s what you need to know about the vaccine.
How it works?
The Oxford University vaccine – or the ChAdOx1 nCoV-19 vaccine – is called a viral vector vaccine. This class of vaccine uses another type of virus as the vehicle for genetic data for Covid-19.
In this case, the ChAdOx1 vaccine uses a weakened chimpanzee adenovirus, which causes the common cold in chimpanzees. The genetic code of this virus is changed so that it does not reproduce in humans. Scientists added the genetic sequence of the coronavirus surface spike protein to the viral vector, so that the spike protein is produced when the vaccine enters a person’s cells. This then induces an immune response, so that the immune system will fight the coronavirus if the person is infected.
This is because the vaccine mimics the coronavirus and causes the immune system to respond if the person later contracts the coronavirus.
Who makes the vaccine?
This vaccine is developed by the Jenner Institute at the University of Oxford and the Oxford Vaccine Group. The team, which began work in January 2020, is led by Professors Sarah Gilbert, Andrew Pollard, Teresa Lambe, Catherine Green and Adrian Hill, and Dr Sandy Douglas.
The Oxford team was well equipped to develop this vaccine. They were already using the adenovirus to test a vaccine against Middle East Respiratory Syndrome (Seas), another type of coronavirus, showing that it protected sea monkeys and was safe for humans. They had also produced vaccine candidates against influenza and the Zika virus using the same technology.
The University of Oxford has entered into a license agreement with AstraZeneca, an Anglo-Swedish pharmaceutical company, to market, distribute and produce the vaccine if it proves effective.
What do we know so far if it works?
A Phase I / II trial suggested the vaccine was safe, without serious side effects, and generated a strong immune response.
The trial began in the UK in April, with more than 1,000 healthy adult volunteers having received either the candidate vaccine or a meningitis vaccine. The results of the trial, published in late July in the Lancet medical journal, showed that the vaccine elicited a T cell response within 14 days of vaccination and an antibody response within 28 days. T lymphocytes are white blood cells that can attack infected cells. Antibodies can neutralize a virus.
Ten of the trial participants received two doses of the vaccine. They had an even greater immune response – which might suggest that an initial vaccine followed by a booster would be a solution.
Professor Sarah Gilbert, of the Jenner Institute, told The Guardian her team was “really happy” with the results.
“We have a lot of experience using this technology to make other vaccines, so we knew what we expected to see, and this is what we saw,” she said.
But while experts agree the results were promising, they say there is still a long way to go before whether the vaccine can guard against Covid-19.
What tests are currently underway?
The next step is a Phase III trial, a larger trial to see if the vaccine will protect people against the virus. This is the last step before approval.
In phase III trials, which measure the effectiveness of a vaccine, thousands of volunteers receive the vaccine or a control. Scientists then monitor infection rates, looking for a disparity between the two groups (as well as possible rare side effects). According to the World Health Organization, a vaccine would need to lower the disease rate by at least 50% to be approved.
For the trial to be most effective and for the necessary data to be collected quickly, volunteers must have some chance of contracting the virus, for example, because they live in a place with high transmission. Trials in Brazil and the United States can therefore be particularly useful. In the ongoing UK trial, people who have a higher risk of exposure to Covid-19, such as healthcare workers, will be prioritized.
A number of phase III trials of the Oxford vaccine are underway internationally:
- A Phase II / III trial aims to recruit up to 10,560 adults and children across the UK.
- A phase III trial in the United States is seeking 30,000 participants.
Brazil launched a phase III trial of the vaccine in June, which will recruit 5,000 volunteers.
A team in South Africa is seeking to recruit 2,000 people to test the vaccine.
When will he be ready?
It’s hard to say when the virus might be ready for distribution if it’s proven to work in Phase III trials.
The duration of a phase III trial depends on the levels of transmission. According to the team at the University of Oxford, if transmission remains high, they might get enough data to judge whether the vaccine works “in a few months” – but it will take longer (up to six months) if transmission levels decrease.
Who will buy it?
Although the vaccine has not yet validated trials and received regulatory approval, several agreements have already been made to distribute the vaccine. The Australian government has signed a letter of intent with AstraZeneca to obtain 25 million doses of the vaccine if it allows trials.
The UK has reached a deal to get up to 30 million doses immediately. Under an agreement with the European Alliance for Inclusive Vaccines, Europe would receive up to 400 million doses. The company has also agreed to supply 300 million doses to the United States.
The Serum Institute of India has agreed to produce 1 billion doses for low and middle income countries.