Fresh hopes for a vaccine to protect against Covid-19 emerged today.
romising early stage results from a clinical trial of the UK’s vaccine candidate against the virus have been published in the Lancet.
A phase two trial on another possible vaccine in China also found it is safe and induced an immune response, according to the medical journal.
The vaccine is called AZD1222 and is being developed by AstraZeneca and scientists at Britain's University of Oxford.
The early stage UK trial finds that the vaccine is safe, causes few side effects, and induces strong immune responses in both parts of the immune system – provoking a T cell response within 14 days of vaccination.
"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," vaccine developer Sarah Gilbert said.
"We still do not know how strong an immune response we need to provoke to effectively protect against SARS-CoV-2 infection."
Gilbert said researchers needed to learn more about Covid-19 and continue late stage trials which have already commenced.
An ideal vaccine against SARS-CoV-2 should be effective after one or two vaccinations, work in target populations including older adults and those with other health conditions, confer protection for a minimum of six months, and reduce onward transmission of the virus to contacts.
The current trial is too preliminary to confirm whether the new vaccine meets these requirements, but phase 2 (in the UK only) and phase 3 trials to confirm whether it effectively protects against SARS-CoV-2 infection are happening in the UK, Brazil and South Africa.
Explaining how the vaccine works, study lead author Professor Andrew Pollard, University of Oxford, UK, says: “The new vaccine is a chimpanzee adenovirus viral vector (ChAdOx1) vaccine that expresses the SARS-CoV-2 spike protein.
It uses a common cold virus (adenovirus) that infects chimpanzees, which has been weakened so that it can’t cause any disease in humans, and is genetically modified to code for the spike protein of the human SARS-CoV-2 virus. This means that when the adenovirus enters vaccinated people’s cells it also delivers the spike protein genetic code. This causes these people’s cells to produce the spike protein, and helps teach the immune system to recognise the SARS-CoV-2 virus.
A phase 2 trial of an Ad5 vectored COVID-19 vaccine candidate, conducted in China, has found that the vaccine is safe and induces an immune response, according to new research published in The Lancet.
The randomised trial sought to evaluate the safety and immunogenicity of the vaccine candidate and follows a phase 1 trial published in May 2020 . The results provide data from a wider group of participants than their phase 1 trial, including a small sub-group of participants aged over 55 years and older, and will inform phase 3 trials of the vaccine.
However, the authors note that it is important to stress that no participants were exposed to SARS-CoV-2 virus after vaccination, so it is not possible for this study to determine whether the vaccine candidate effectively protects against SARS-CoV-2 infection.
Professor Feng-Cai Zhu, Jiangsu Provincial Centre for Disease Control and Prevention, China, says: “The phase 2 trial adds further evidence on safety and immunogenicity in a large population than the phase 1 trial. This is an important step in evaluating this early-stage experimental vaccine and phase 3 trials are now underway.”
AZD1222 was developed by Oxford university and licensed to AstraZeneca, which has put it into large-scale, late-stage trials to test its efficacy. It has also already signed deals to produce and supply over 2 billion doses of the shot.
The new trial included 1,077 healthy adults aged 18-55 years with no history of Covid-19.
"Today's data increases our confidence that the vaccine will work and allows us to continue our plans to manufacture the vaccine at scale for broad and equitable access around the world," said Mene Pangalos, Executive Vice President of BioPharmaceuticals Research and Development at AstraZeneca.
With additional reporting from Reuters
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