Data from more than 1,000 healthy volunteers dosed with a coronavirus vaccine developed at Oxford University and AstraZeneca suggest the shot is safe and stimulates an immune response against the virus.
The first phase 1/2 results with the ChAdOx1 vaccine – also known as AZD122 – were published today in medical journal The Lancet and bode well for the outcome of much larger phase 2 and 3 trials that are already underway in the UK, Brazil and South Africa, say the investigators, led by Prof Andrew Pollard of Oxford University.
The data reveal that ChAdOx1 generated antibodies that were able to neutralise the SARS-CoV-2 virus in more than 90% of subjects aged 18 to 55 after a single dose, and 100% after two doses.
All vaccinated patients also showed increases in white blood cells (T cells) that can fight the infection and are thought to be an important factor in limiting the severity of COVID-19-related illness.
There were minimal side effects such as headache and fever, which could be prevented with paracetamol, according to the researchers.
AstraZeneca’s share price ticked up by almost 2% following the announcement.
ChAdOx1 is based on an adenoviral vector based on a weakened version of the adenovirus that causes a common cold-line illness in chimpanzees, containing the genetic material of SARS-CoV-2 spike protein.
“The immune responses observed following vaccination are in line with what we expect will be associated with protection against the SARS-CoV-2 virus, although we must continue with our rigorous clinical trial programme to confirm this,” commented Prof Pollard.
Meanwhile, The Lancet also carries a 500-patient, phase 2 study from researchers in China on another adenoviral vector-based vaccine developed by CanSino Biologics, which also generated antibody and T cell responses and appeared to be safe.
An editorial accompanying the studies by Naor Bar-Zeev and William Moss at Johns Hopkins Bloomberg School of Public Health in the US notes that the results of the two trials “are broadly similar and promising”.
They add however that “much remains unknown about these and other COVID-19 vaccines in development, including longevity of response and immunogenicity in older adults or other specific groups.”
At the moment the follow-up period in both studies is vanishingly short in the context of typical vaccine studies, but it’s nevertheless encouraging that in the Oxford study the data show sustained immune responses for up to 56 days.
Some scientists estimate that vaccine protection for just six months or more could be enough to have an impact in controlling the coronavirus pandemic.
Larger studies are needed to conform these early findings and answer other key questions, such as how the vaccines perform in older people, those with concomitant illnesses and other high-risk individuals, and children.
Meanwhile, there have also been calls for so-called “challenge studies”, which would involve deliberately infecting subjects with SARS-CoV-2 after a vaccine to test directly the level of protection it confers.
Oxford University has partnered with AZ to produce the ChAdOx1 vaccine, and the UK government has already placed an order for 100m doses, with other big orders also received from the US, German, France and others.
The UK government has also just ordered 90 million doses of two other COVID-19 vaccines – from BioNTech/Pfizer and Valneva – plus an option for another 40 million doses.
Pfizer and BioNTech also announced further clinical data from the most advanced from a group of four vaccines they are developing, with data collected in Germany supporting findings of a US trial arm published earlier this month.
According to the latest estimates from the World Health Organization there are 23 potential vaccines in clinical trials and 140 in preclinical development.
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