First peer-reviewed results of phase 3 human trials of Oxford vaccine demonstrate efficacy | University of Oxford

First peer-reviewed results of phase 3 human trials of Oxford vaccine demonstrate efficacy

8 December 2020

  • Researchers show overall vaccine efficacy of 70.4% from a pooled analysis of two-dose regimen
  • No hospitalisations or severe disease observed in the vaccinated groups from three weeks after first dose
  • Efficacy results are based on data taken from 11,636 volunteers across the United Kingdom and Brazil
  • Data are first Phase 3 trial results of a coronavirus vaccine to be published in peer-review literature


Today [08/12/20] University of Oxford and AstraZeneca researchers present a pooled analysis of Phase 3 trials of a vaccine against SARS-CoV-2 across two different dose regimens, resulting in an average efficacy of 70.4%.

The new study published in theLancetis the first peer-reviewed publication of phase 3 data from studies of a vaccine against the coronavirus.

The efficacy data are based on 11,636 volunteers across the United Kingdom and Brazil, and combined across three groups of people vaccinated – two groups who received a standard dose prime vaccination followed by a standard dose booster vaccination and one group (in the UK only) who received a low dose prime vaccination followed by a standard dose vaccination.

Professor Andrew Pollard, Director of the Oxford Vaccine Group and Chief Investigator of the Oxford Vaccine Trial, said: “Today, we have published the interim analysis of the phase III trial and show that this new vaccine has a good safety record and efficacy against the coronavirus. We are hugely grateful to our trial volunteers for working with us over the past 8 months to bring us to this milestone.”

The pooled analysis in the study shows that the overall vaccine efficacy at least 14 days after the second dose was 70.4%; the standard dose / standard dose sub-groups showing 62.1% efficacy, and with the low dose / standard dose sub-group demonstrating 90.0% efficacy. No hospitalisations or severe disease were observed in the vaccinated groups.

The authors further report on an extensive safety database from volunteers in the UK, Brazil and South Africa accompanying the efficacy findings; of over 23,000 trial volunteers, and over 74,000 ‘person-months’ of safety follow up, only three from 175 reported serious adverse events were possibly related to the vaccine. The trial protocols, and statistical analysis method are presented in the appendices to the paper.

Of these, one was considered ‘possibly related’ to the ChAdOx1 nCoV-19 vaccine, one occurred in the control group, and a further case of severe fever in the vaccinated group was considered to be an expected vaccine-related event.

Of the 11,636 volunteers in the UK and Brazil included in this initial analysis of efficacy, the majority are in the 18-55 age range (UK 87% and Brazil 90%), with those aged 56 or older contributing 12%. As only five cases included in the primary analysis occurred in those who were more than 55 years old, the vaccine efficacy in older age groups could not be assessed but will be determined in future analyses after more cases have accrued in this age range.

Professor Sarah Gilbert, Professor of Vaccinology at the University of Oxford, said:
“We have known for many years that adenoviral vectored vaccines fulfil the requirements for use against outbreak or pandemic diseases. They are safe, highly immunogenic, can be manufactured in large quantities at low cost and do not require frozen storage. Following the demonstration of vaccine efficacy in many preclinical studies, we now have clear evidence of efficacy in the trial results presented in a peer-reviewed publication today. Now under regulatory review, we hope that this vaccine will shortly be in use to start saving lives.”

The researchers also investigated the potential for the vaccine to prevent asymptomatic disease, through the use of weekly swabbing by UK trial volunteers. These data indicate that the low dose / standard dose vaccine may provide a protection against asymptomatic infection, but stress that these data are at an early phase, with too high a level of uncertainty to be certain that this vaccine will protect against asymptomatic infection.

Pascal Soriot, Chief Executive Officer, said: “Today’s peer-reviewed publication enables a full disclosure of the Oxford program interim analysis. The results show that the vaccine is effective against COVID-19, with in particular no severe infections and no hospitalisations in the vaccine group, as well as safe and well tolerated. We have begun submitting data to regulatory authorities around the world for early approval and our global supply chains are up and running, ready to quickly begin delivering hundreds of millions of doses on a global scale at no profit.”

Further analysis is ongoing into these data, and will be provided to the regulators to enable them to best decide on dose protocols, should this vaccine be granted emergency use authorisation.

Notes to editors: 

For access to the Article and Comment, please see: http://www.thelancet-press.com/embargo/oxfordphase3.pdf 
For access to the Appendices, please see: http://www.thelancet-press.com/embargo/oxfordphase3APPX.pdf 
Live link: http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)32661-1/fulltext 

For further information or to arrange an interview, please contact the University of Oxford press office at news.office@admin.ox.ac.uk or on +44 (0)1865 280528. 

For more about the Oxford vaccine project and team: www.ox.ac.uk/covid-vaccine 

Previous papers published on this project: 

For detailed information about the vaccine trial: covid19vaccinetrial.co.uk 

Images: Credit: University of Oxford, John Cairns 

Video: 
Downloadable researcher interviews and b-roll for video editors and broadcast: 
https://vimeo.com/showcase/7803812 
Password: Please contact the University of Oxford press office at news.office@admin.ox.ac.uk or on +44 (0)1865 280528. 
NOTE: These are for downloading and editing by media outlets, not for uploading or using wholesale. 

Short explainer video for social media or embed: https://youtu.be/xHJ_RqeXXy0 

About the Oxford COVID-19 vaccine 
ChAdOx1 nCoV-19, now known as AZD1222 co-invented by the University of Oxford and its spin-out company, Vaccitech, is being trialled by the University’s Jenner Institute and Oxford Vaccine Group. The team started working to develop a vaccine against coronavirus in January 2020. 

Developed at the Jenner Institute, the recombinant adenovirus vector ChAdOx1 nCoV-19 uses a viral vector based on a weakened version of the common cold virus (adenovirus) containing the genetic material of SARS-CoV-2 spike protein. After vaccination, the surface spike protein is produced, which primes the immune system to attack COVID-19 if it later infects the body. 

Vaccines made from the ChAdOx1 nCoV-19 virus have been given to around 11,000 people to date and have been shown to be safe and well tolerated, although they can cause temporary side effects, such as a temperature, flu-like symptoms, headache or sore arm. 

The potential vaccine entered Phase III clinical trials in May to study safety and efficacy in healthy volunteers aged 18 to 55 years, across 19 trial sites in the UK. The University of Oxford is also working with research partners at a number of clinical trial sites around the world as part of this late stage trial. 

Not for profit information: 
As part of our agreement with our partner AstraZeneca, the vaccine will be supplied on a not-for-profit basis for the duration of the pandemic and in perpetuity for low- and middle-income countries. 

Acknowledgements: 
This trial is funded by the National Institute for Health Research, UK Research and Innovation, the Bill & Melinda Gates Foundation, the Lemann Foundation, and the South African Medical Research Council. We are grateful to the NIHR infrastructure provided through the NIHR Biomedical Research Centres and the NIHR Clinical Research Network at the UK study sites. 

Oxford University 
Oxford University has been placed number 1 in the Times Higher Education World University Rankings for the fifth year running, and at the heart of this success is our ground-breaking research and innovation. 

Oxford is world-famous for research excellence and home to some of the most talented people from across the globe. Our work helps the lives of millions, solving real-world problems through a huge network of partnerships and collaborations. The breadth and interdisciplinary nature of our research sparks imaginative and inventive insights and solutions. 

Through its research commercialisation arm, Oxford University Innovation, Oxford is the highest university patent filer in the UK and is ranked first in the UK for university spinouts, having created more than 200 new companies since 1988. Over a third of these companies have been created in the past three years.