The potential vaccine prompted a protective immune response in hundreds of people who participated in the early trial.
UK phase 2 vaccine trial shows promise
Preliminary results from tests of an experimental coronavirus vaccine in the UK suggest that it prompts a protective immune response, scientists from the University of Oxford said. The observations on the Astra Zeneca product were published in the scientific journal The Lancet.
The experimental COVID-19 vaccine produced a dual immune response in people aged 18 to 55 that lasted at least two months after they were immunized, scientists said.
”We are seeing good immune response in almost everybody,” said Dr. Adrian Hill, director of the Jenner Institute at the University of Oxford. ”What this vaccine does particularly well is trigger both arms of the immune system,” he added.
Scientists said the vaccine also caused a reaction in the body’s T-cells which help to fight off the coronavirus.
”There’s increasing evidence that having a T-cell response as well as antibodies could be very important in controlling COVID-19,” Hill said and suggested that the immune response might be boosted after a second dose.
But it also caused some minor side effects, such as fever, chills and muscle pain more often than in those who were instead given a control meningitis vaccine.
British researchers first began testing the vaccine in April in some 1,000 people, half of whom got the experimental vaccine, while the others got the meningitis vaccine. The results are part of the second phase of the clinical development process. The vaccine will now need to undergo a phase three, where it will be administered to thousands of people and tested for efficacy and safety. A fourth phase, once it has been approved and licensed, usually involves further ongoing studies and monitoring.
Hill estimated that there could be sufficient data by the end of the year to decide if the vaccine should be adopted for mass vaccination campaigns.
”There was a hope that if we had a vaccine quickly enough, we could put out the pandemic,” Hill said, noting the continuing surge of infections globally. ”I think it’s going to be very difficult to control this pandemic without a vaccine.”
Several countries including Germany, France, the Netherlands, Italy, U.S. and the U.K. have all signed deals to receive hundreds of millions of doses of the vaccine.
Speaking at a webinar organised by the Science Media Centre, Prof Adrian Hill, director of the Jenner Institute for Vaccine Research at Oxford University, said the early success of the Oxford vaccine was good news for other teams trying to develop a Covid-19 vaccine around the world. He said:
The good news is that these vaccines that are in development – 23 of them now – fall into groups. If our vaccine works it is much more likely that another adenoviral vaccine would work as well …
It is perhaps a little scientifically unlikely that one vaccine would be perfect and all the others would fail, so if one worked well, similar vaccines have a good chance of working.
He also said was very unlikely that any immunity to Covid-19 provided by the vaccine would only be short-term. He explained:
Making the assumption that if natural infection doesn’t give you immunity for very long, therefore a vaccine won’t give you immunity for very long – that doesn’t follow.
What matters is the type of vaccine technology you are using.
The other upbeat response is that there aren’t really vaccines out there that just last for a few months – by and large vaccines last for some years, or at least a year and then you might need a top-up. [Immunity] is not going to disappear very quickly.
At the webinar Prof Andrew Pollard, of the Oxford Vaccine Group, said it was impossible to say yet how many shots of the vaccine each age group would need to be given to gain and then maintain levels of coronavirus immunity. He said:
We have seen encouraging response with one dose.
But in the small subgroup that you see in the Lancet paper, there are better responses with two doses – that is not totally unexpected.
We know that human populations are completely naive to this virus and so you need quite a heavy lift in order to get a really good immune response from this vaccine, which is what we are trying to achieve with the two-dose schedule.
And Prof Sarah Gilbert, professor of vaccinology at Oxford University, told the webinar why scientists were trying to stimulate both antibodies and a T-cell response through a Covid-19 vaccine. She said:
Antibodies are in fluids in the body and they can encounter viruses when they first come into the body.
Antibodies can bind on to the outside of the virus to stop them infecting cells – so that’s what we mean by neutralising antibodies.
It sees the virus, attaches to it as soon as it comes into the body and stops it causing any infection.
T-cells can recognise which cells have the virus inside them and destroy them to prevent further spread of the virus in the body.
The two systems working together are completely complementary, first of all stopping infection coming in, and if [the virus] does get past the antibodies, [T-cells] destroy the cells that the virus has taken over.