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Oxford COVID-19 vaccine 70% effective

Published: 23 November 2020

The NIHR-funded and supported ChAdOx1 nCoV-2019 vaccine, developed by University of Oxford and AstraZeneca, is effective at preventing COVID-19 and offers a high level of protection, according to international research in more than 24,000 participants.

An interim analysis of data from Phase III trials shows that the vaccine, which is administered in two doses, was 70.4% effective. The vaccine was 90% effective if administered at a half dose and then at a full dose, or 62% effective if administered in two full doses.

The data also showed lower rates of asymptomatic infection in the people who had received the half dose then full dose regimen, which suggests that the vaccine could help to prevent transmission of the virus.

No serious safety events related to the vaccine were identified, with no participant admitted to hospital or experiencing severe side effects.

The clinical trials have enrolled more than 24,000 participants so far from diverse racial and geographical groups in the UK, Brazil and South Africa. The trials will now continue to final analysis. 

The interim Phase III data builds on the Phase I/II trial results, which have shown that the vaccine induces strong antibody and T cell immune responses across all age groups, including older adults, and has a good safety profile. 

The research has received funding from the NIHR and UK Research and Innovation. Recruitment and delivery of all phases of the research in the UK have been supported by the NIHR Clinical Research Network.

Read more about NIHR COVID-19 research

Professor Andrew Pollard, Director of the Oxford Vaccine Group and Chief Investigator of the Oxford Vaccine Trial, said: “These findings show that we have an effective vaccine that will save many lives. Excitingly, we’ve found that one of our dosing regimens may be around 90% effective and if this dosing regime is used, more people could be vaccinated with planned vaccine supply. Today’s announcement is only possible thanks to the many volunteers in our trial, and the hard working and talented team of researchers based around the world.”

Professor Sarah Gilbert, Professor of Vaccinology at the University of Oxford, said: “The announcement today takes us another step closer to the time when we can use vaccines to bring an end to the devastation caused by SARS-CoV-2. We will continue to work to provide the detailed information to regulators. It has been a privilege to be part of this multinational effort which will reap benefits for the whole world.”

Both the interim Phase III efficacy data and the extensive safety data will be submitted to all regulators across the world - including in the UK - for independent scrutiny and product approval, including for emergency use. Many of these regulators have been reviewing the trial data on a rolling basis during the trial. 

In parallel, the full analysis of the Phase III interim data are being submitted for independent scientific peer review and publication. 

Further trials are being conducted in the United States, Kenya, Japan and India. The trial team expects to have under 60,000 participants by the end of the year. These trials will provide regulators with further information about the efficacy and safety of the Oxford vaccine, including its ability to both protect against and stop the transmission of COVID-19. 

The Oxford vaccine (ChAdOx1 nCoV-19) is made from a weakened version of a common cold virus (adenovirus) that has been genetically changed so that it is impossible for it to grow in humans.  

Adenovirus vaccines are stable and easily manufactured, transported and stored at domestic fridge temperature (2-8 degrees C). This means they can be easily distributed using existing medical facilities such as doctor’s surgeries and local pharmacies, allowing for the vaccine, if approved, to be deployed very rapidly.

AstraZeneca already has international agreements in place to supply three billion doses of the vaccine, with access being built through more than 30 supply agreements and partner networks. The vaccine will be provided on a not-for-profit basis for the duration of the pandemic across the world, and in perpetuity to low- and middle-income countries.

Read more on the Oxford University breakthrough

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