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Oxford COVID-19 vaccine trial results confirm it is safe and effective

Updated: Jan 22, 2021

The interim analysis data for the Oxford-AstraZeneca vaccine trial for COVID-19 has been published in The Lancet, following a press release a couple of weeks ago.

Dosing differences

The results show that the ChAdOx1 nCoV-19 vaccine is safe and effective, with an average effectiveness of 70%.

This is the average of results from two different dosing schedules – two higher dose injections showing 62% protection, and one lower dose jab followed later by a higher dose which provided 90% protection.

That surprising result was based on data from only 1,367 of the 11,636 participants (7548 in the UK, 4088 in Brazil), after a manufacturing issue resulted in a batch of lower strength doses. The Medicines and Healthcare products Regulatory Authority agreed this batch should still be used in the trial, yielding what appears to be a lucky find.

Those small numbers mean that although the published data indicates that the vaccine is safe and effective, it’s hard to draw firm conclusions about the seemingly more effective dosing schedule.

This is especially true for over 55s, none of whom were given that dose - although earlier trial results reported in The Lancet showed the vaccine is safe and produces strong immune responses in older people, thanks to 240 over 70s in Southampton who provided the data for this higher-risk age group.

What happens next?

The Medicines and Healthcare Regulatory Agency (MHRA) are considering whether to approve the vaccine - a key regulatory step before it can be distributed and given to patients.

The UK government has pre-ordered 100 million doses of the Oxford-AstraZeneca vaccine, enough to immunise 50 million people - or more if the schedule using the lower dose first is recommended.

The vaccine, known as ChAdOx1 nCoV-19, is made from a weakened version of a common cold virus (adenovirus) from chimpanzees that has been genetically changed so that it is impossible for it to grow in humans.This has been combined with genes that make ‘spike protein’ from the COVID-19 virus (SARS-CoV-2), which plays an essential role in the infection pathway of the virus. It is relatively cheap to produce in large quantities, and can be stored at fridge temperature, which makes it easier to distribute across the NHS and globally.

Work on COVID-19 vaccines continues to be of great importance, to give the best range of options and the best ways of using each vaccine. You can sign up to the NHS vaccine registry to be contacted about taking part in COVID-19 vaccine studies in the UK, including in Southampton

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