The human trial of COVID-19 vaccine candidate developed by the University of Oxford and backed by AstraZeneca Plc has shown a positive result. Officially known as AZD1222, the vaccine has prompted a protective immune response in hundreds of people who got the shot, according to a report published in British medical journal Lancet. The vaccine did not prompt any serious side effects, the journal said.
The researchers said that they found their experimental COVID-19 vaccine produced a dual immune response in people aged 18 to 55. “We are seeing good immune response in almost everybody,” said Dr Adrian Hill, director of the Jenner Institute at Oxford University. “What this vaccine does particularly well is trigger both arms of the immune system,” he said.
Hill said that neutralizing antibodies are produced — molecules which are key to blocking infection. In addition, the vaccine also causes a reaction in the body’s T-cells which help to fight off the coronavirus.
The vaccine uses a weakened version of chimpanzee adenovirus as a vector, infused with the genetic material of SARS-CoV-2 spike protein. Explaining how the Oxford 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.”
The potential vaccine is already in large-scale phase III human trials to assess whether it can protect against COVID-19. In phase-3, it will be tested on roughly 30,000 people in the US alone.
Hill estimated they might have sufficient data by the end of the year to decide if the vaccine should be adopted for mass vaccination campaigns.
He said the vaccine seemed to produce a comparable level of antibodies to those produced by people who recovered from a COVID-19 infection and hoped that the T-cell response would provide extra protection.
“There’s increasing evidence that having a T-cell response as well as antibodies could be very important in controlling COVID-19,” Hill said. He suggested the immune response might be boosted after a second dose; their trial tested two doses administered about four weeks apart.
Hill said Oxford’s vaccine is designed to reduce disease and transmission. “We hope this means the immune system will remember the virus, so that our vaccine will protect people for an extended period,” Pollard said.
“However, we need more research before we can confirm the vaccine effectively protects against SARS-CoV-2 (COVID-19) infection, and for how long any protection lasts,” he said.
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