An effective and readily available coronavirus vaccine is slated as the greatest hope of getting Australia, and the world, to the other side of this pandemic.
Earlier this month the Australian government reached an agreement with UK-based drug company AstraZeneca, which is now working on stage three human trials of a vaccine – ChAdOx1 nCoV-19 – with Oxford University.
It is one of a handful of the COVID-19 vaccine candidates that have entered the more advanced stages of clinical trials.
University of Tasmania Infectious Disease Specialist Katie Flanagan, who completed her PhD at Oxford University, has led multiple vaccine immunology trials throughout the world, including vaccines developed by the same group in Oxford.
Here, she explains what the agreement could mean for us.
Talk us through the deal
The agreement reached is a ‘letter of intent’, so the deal will only go ahead if the vaccine is proven to be efficacious in ongoing clinical trials.
The Oxford vaccine uses a chimpanzee virus carrying the code for a key COVID-19 protein.
The virus enters human cells which can then produce the virus protein and mount an immune response against it.
If the Oxford is found to protect against COVID-19, the CSL laboratories in Melbourne would start to manufacture it.
What are the results from early clinical trials?
The preliminary phase 1 and 2 human trial results have been published recently in The Lancet journal, in which 543 people received one dose of the vaccine.
The study showed that the vaccine is safe, but does stimulate local and systemic reactions, such as pain, tenderness and fatigue, in the majority of people receiving the vaccine.
Fortunately, there were no severe side effects of vaccination.
The other important thing to point out is that chimpanzee adenovirus vaccines for other infections have been shown to be safe in previous clinical trials conducted by the Oxford group in adults and children.
The published study also showed that the Oxford vaccine induces neutralising antibodies which can potentially prevent the virus entering human cells.
It also induced specialised cells called T cells which can help protect against viral infection.
The antibody responses were at the same level as the people who have recovered from COVID-19, suggesting they are sufficient to be protective.
However, we don’t know yet whether the vaccine protects against COVID-19 and will have to await the results from ongoing phase 3 trials.
How does the Oxford vaccine compare to others in the pipeline?
I would say it’s one of the front-runners.
There are over 200 [vaccine candidates] that are in development and 30 of them have progressed to human clinical trials.
The majority of candidates in human trials are in phases 1 and 2, which involves testing for safety and immunogenicity in hundreds of donors.
Eight candidate vaccines have now entered phase 3 trials in tens of thousands of individuals.
All the vaccine candidates in phase 3 trials have good safety profiles and stimulate antibodies and T cells.
So any or all of these vaccines may turn out to protect against COVID-19.
What’s the timeline?
In the phase 3 studies being conducted in Brazil, India and UK, tens of thousands of people are being immunised with the Oxford vaccine.
The researchers will analyse whether the Oxford vaccine is protective against COVID-19.
In these studies, individuals are randomised to get the vaccine or not.
They are then followed up to see who gets COVID-19 and other factors such as hospitalisation and death among the vaccinated and unvaccinated groups.
Progress will therefore depend on how many people get vaccinated, how quickly, and how much circulating virus there is in the community to see if it protects those who get the vaccine.
The phase three trials will probably continue through to next year.
However, the researchers may be able to do an interim analysis if they recruit enough people and see enough cases of COVID-19.
I anticipate that by the end of this year, possibly in a couple of months, we will be getting our first signals as to whether the Oxford vaccine is working.
This may allow interim approval for manufacturing and administration.
However, a major hurdle will be the logistics of manufacturing and distributing the vaccine.
So in reality, we are probably talking the middle of next year before any vaccines will be available for widespread use.
Will it be the answer?
The first thing to say is that about 95 per cent of vaccines that get developed don’t actually work.
But since we’ve got more than 200 candidates in the pipeline, and 5 per cent work, we would imagine we will end up with a handful of vaccines that are actually efficacious.
The Oxford vaccine looks promising, but no more so than many of the other candidates, so we may end up with several vaccines to choose from.
What we don’t know is how long the various candidates will provide protection for.
We also don’t know if the vaccines will provide full protection or partial protection.
It’s unlikely we are going to get a vaccine that is 100 per cent protective against the disease.
But it will hopefully decrease disease severity, hospitalisation and death.
Influenza vaccine is only about 50 per cent efficacious, yet it decreases disease severity and helps control the number of infections in the community.
How will it help?
Currently, 80 percent of people with COVID-19 have a mild illness or are asymptomatic, while 20 percent require hospitalisation and approximately 5 per cent may need ICU care.
If the proportion of people with severe illness can be reduced by vaccinating them, then our hospitals will be able to cope and less people will die.
The aim is to get a high level of immunity in the population, called herd immunity, in order to reduce the amount of virus circulating among people.
It is difficult to predict what will actually happen in the face of widespread vaccination.
Older people and those with immunocompromise, for example, may not respond as well to the vaccine.
But the hope is that transmission and less people will require hospital care, allowing us to start looking at a post-COVID era, where people get back to a more normal lifestyle.
What is the key to being in a position to develop a successful vaccine?
For the Oxford group it comes down to comes down to the fact that the group have been developing vaccines for more than 25 years.
They already had the chimpanzee vaccine platforms ready to go.
They had the manufacturing capacity and the infrastructure to progress rapidly into pre-clinical and then phase 1-2 human trials, as soon as the virus was sequenced.
They had already developed a vaccine based on the same platform for another coronavirus, MERS [Middle East Respiratory Syndrome], and had tested it in a phase 1 trial in humans.
So it was actually quite quick and easy for them to get a SARS-CoV-2 vaccine made and advance into human clinical trials.
Are you optimistic?
From a point of view of vaccines I am very optimistic that we will get a vaccine that works.
The effort and pandemic speed at which vaccines are being developed is totally unprecedented and incredibly impressive.
The funds and the international effort and collaboration going into this is extraordinary.
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