COVID-19 vaccine is safe and stimulates the body's immune defences

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Initial trials of the University of Oxford-developed ChAdOx1 nCoV-19 vaccine have shown it is safe and induces an immune response.

Results from the first two phases of a vaccine trial involving 1,077 people, published in The Lancet, show those who had the vaccine made antibodies and T-cells that can fight coronavirus.

A Southampton team, led by Professor Saul Faust, are already involving people from the city and region in delivering the next phase of the trial, which will enrol over 10,000 volunteers across the UK, to evaluate the vaccine’s potential in protecting people from infection.

The UK has already ordered 100 million doses of the vaccine.

What did they find?

Southampton was one of five trial sites across the UK. In total, 1,077 healthy adults who had not tested positive for the virus and were 18–55 years of age took part.

Half of the volunteers in the study were injected with the COVID-19 vaccine, while the other half received an existing meningitis vaccine as a ‘control’, to provide a comparison of immune response.

Neither the participants nor the doctors or nurses administering it knew which vaccine they had been given, to avoid biasing in the results. A separate data team tracked the results as they came in.

Ten participants were given a second ‘booster’ dose of the COVID-19 vaccine 28 days after the first. These participants knew which vaccine they had been given.

The researchers detected antibody responses to the virus in 91% (32 of 35) participants after 28 days, and this was further boosted in all ten participants after the second dose.

They also showed that T-cells, another part of the immune system which works together with antibodies, increase in response to the vaccine.

How does the vaccine work?

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.

The intention is that the immune system responds to the vaccine as if it is coronavirus, providing future protection if the person later catches the virus.

What next?

While the researchers have now shown the immune system responds to the vaccine, it is not yet clear if this protects people from getting ill or passing it on.

The next phase of the trial is already underway, with a target of over 10,000 participants in Oxford, Southampton and across the UK. Older people are far more vulnerable to COVID-19, and  in Southampton the phase 2 trial has so far recruited 240 people over 70 years old in an important component of the study to investigate whether older people’s immune system can also respond well enough to the vaccine to be able to provide protection.

With the numbers of cases in the UK now falling, it is becoming increasingly difficult to get enough people infected with coronavirus to tell if it works, so this phase of the trial has been expanded to also include 30,000 people in the USA, 2000 in South Africa and 5000 in Brazil.

Posted on Friday 24 July 2020