The vaccine, which is being developed in partnership with AstraZeneca, was found to be 70.4% effective across two dosing regimens. However, higher efficacy of 90% was found in a regimen which used a half first dose and a standard second dose. In those that received two full doses the vaccine was shown to be 62% effective.
The phase 3 interim analysis included 131 COVID-19 cases among participants who either received the vaccine or a a licensed MenACWY vaccine. There were no serious or hospitalised cases of COVID-19 in those who had received the COVID vaccine.
The researchers said that the trial also showed that the vaccine could reduce virus transmission because there had been a reduction in observed asymptomatic cases.
They added that the interim phase 3 results backed up previously reported phase 2 data, which have shown strong antibody and T cell immune responses in all age groups, including older adults. No safety concerns relating to the vaccine have been reported throughout the trials.
The university confirmed it would be submitting its phase 3 interim results and safety data to the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK, and other regulators around the world, so the vaccine could be approved for use.
The government has invested heavily in the Oxford vaccine and has orders in place for 100m doses of the jab. The UK is expected to receive 4m doses of the vaccine before the end of the year, which means it could be used in the early stages of the COVID-19 vaccination programme if approved.
Unlike the Pfizer/BioNTech vaccine, which needs to be stored at -70 degrees Celsius and only has an active life of four-five days once thawed, the Oxford vaccine can be stored at standard fridge temperatures.
It is also understood to be significantly cheaper than the Pfizer/BioNTech and Moderna vaccines, which are based on mRNA technology and have been shown to be 95% and 94.5% effective respectively in phase 3 trials.
Health secretary Matt Hancock confirmed in a press briefing at Downing Street on Friday that Pfizer and BioNTech have submitted their data to the MHRA for approval. He said that, if approved, that vaccine could be rolled out in December. The UK is expected to take delivery of 10m doses of the Pfizer/BioNTech jab before the end of the year.
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.'
A government spokesperson said: 'The results from the University of Oxford/AstraZeneca are very encouraging. The independent MHRA will carry out their crucial work to assess whether the vaccine meets robust standards of safety, effectiveness and quality once it receives the full data from Oxford/AstraZeneca.
'If authorised, the NHS will begin to roll out more widely, starting with those most at risk, in line with Joint Committee on Vaccination and Immunisation advice, and taking into account logistics and practicality.'
Overall the UK currently has orders in place for 355m vaccine doses across seven different vaccines, some of which are not expected to become available until later next year.
The University of Oxford and AstraZeneca have committed to making their vaccine available on a not-for-profit basis around the world during the pandemic, a deal which will be ongoing for low- and middle-income countries.