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Vaccine candidate developed by Oxford found safe, induces immune reaction

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The vaccine candidate developed at the University of Oxford is safe and induces immune reaction, preliminary results released and published in the medical journal The Lancet on Monday said, raising hopes for a cure for COVID-19 that has killed tens of thousands and disrupted human activity across the globe.

Explaining how the vaccine works, study lead author Andrew Pollard said: “The new vaccine is a chimpanzee adenovirus viral vector (ChAdOx1) vaccine that expresses the SARS-CoV-2 spike protein. It uses a common cold virus (adenovirus) that infects chimpanzees, which has been weakened so that it can’t cause any disease in humans, and is genetically modified to code for the spike protein of the human SARS-CoV-2 virus”.

“This means that when the adenovirus enters vaccinated people’s cells it also delivers the spike protein genetic code. This causes these people’s cells to produce the spike protein, and helps teach the immune system to recognise the SARS-CoV-2 virus.”

He added: “The immune system has two ways of finding and attacking pathogens – antibody and T cell responses. This vaccine is intended to induce both, so it can attack the virus when it’s circulating in the body, as well as attacking infected cells.”

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“We hope this means the immune system will remember the virus, so that our vaccine will protect people for an extended period. However, we need more research before we can confirm the vaccine effectively protects against SARS-CoV-2 infection, and for how long any protection lasts.”

The early-stage trial finds that the vaccine is safe, causes few side effects, and induces strong immune responses in both parts of the immune system – provoking a T cell response within 14 days of vaccination (ie, a cellular immune response, it could find and attack cells infected with the virus), and an antibody response with 28 days (ie, humoral immune response, it could find and attack the virus when it was circulating in the blood or lymphatic system).

An ideal vaccine against SARS-CoV-2 should be effective after one or two vaccinations, work in target populations including older adults and those with other health conditions, confer protection for a minimum of six months, and reduce onward transmission of the virus to contacts.

The Lancet said the current trial is too preliminary to confirm whether the new vaccine meets these requirements, but phase 2 (in the UK only) and phase 3 trials to confirm whether it effectively protects against SARS-CoV-2 infection are happening in the UK, Brazil and South Africa.

The new trial included 1,077 healthy adults aged 18-55 years with no history of COVID-19, and took place in five UK hospitals between April 23 and May 21, 2020. The data included in the paper covered the first 56 days of the trial and is ongoing.

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The participants either received the new COVID-19 vaccine (543 people) or the meningococcal conjugate vaccine (534 people). 113 participants (56 given the COVID vaccine, and 57 in the control group) were also asked to take paracetamol before and for 24 hours after their vaccination to help reduce vaccine-associated reactions (as the COVID-19 vaccine was given in a high dose to help induce a strong immune response).

All participants gave additional blood samples and underwent clinical assessments to determine if the vaccine was safe and whether it provoked an immune response. Participants were also asked to record any adverse events throughout the trial.

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