The first human trials of a Covid-19 vaccine being developed by researchers at the University of Oxford suggest it is safe and triggers two types of immune response.
It stimulates production of antibodies – proteins that can bind to the virus, preventing it from entering cells and flagging it to immune cells, and “killer” T cells – white blood cells that attack infected human cells, according to phase 1 trial results published by The Lancet on Monday.
Trials involving some 1,077 people showed the injected virus led to them making antibodies and white blood cells that can fight coronavirus, and did not prompt any serious side effects.
It is too soon to know if this is enough to offer protection and larger trials are under way involving 30,000 people.
However, with Covid-19 cases continuing to accelerate, the findings will be greeted with relief around the world as it suggests the vaccine is able to elicit the right type of immune response though more research is necessary.
The Oxford vaccine being developed with AstraZeneca pharmaceutical company is a weakened version of a common cold virus (adenovirus) that causes infections in chimpanzees, that has been genetically changed so it is impossible for it to grow in humans.
"We are seeing very good immune responses, not just on neutralising antibodies but of T-cells as well. We're stimulating both arms of the immune system," said Prof Adrian Hill head of Oxford's Jenner Institute.
The US biotech company Moderna released results last week from an early-stage test that showed its vaccine raised levels of antibodies that fight the virus.
Although stimulating production of neutralising antibodies does not prove a vaccine will be effective, it’s considered an important early step in testing.
“We want other companies to have vaccines that work as well because the world will get more vaccine sooner,” added Prof Hill. “We just feel there is an advantage of having both arms of the immune system stimulated well. We’re very encouraged...I think we’re a bit more confident it should work this week than last week.”
The Oxford vaccine elicited neutralising antibodies after a single dose, confirmed the Irish scientist, which may be an important advantage in quickly raising immunity.
“I don’t read that clearly in the Moderna data,” he said. “I think they need two doses to see plausibly protective neutralising antibodies.”
A large trial is set to begin this month that will test Moderna’s vaccine in a two-shot regimen.
AstraZeneca will also prioritise a two-shot regimen, Dr Hill said, as “it gives higher titres of antibodies, which is important going forward”.
An antibody titer is a test that measures the amount of antibodies in blood.
The Oxford team still hopes its vaccine could be ready by September. The next big steps will be an appraisal of the protection it provides.
The two key questions will be whether the immune response can protect against severe disease, and if so, for how long. The UK government has already ordered 100 million doses of the vaccine.
One issue, however, relates to recent studies which found antibodies in people who have had Covid-19 drop off over a three-month period after infection. A key question is whether the same drop off is seen in antibodies triggered by a vaccine.
Both the Moderna and Oxford vaccines triggered an immune response in a different way to natural infection, meaning this would not necessarily be expected.
But even if antibodies do wane, the body might still be able to produce them much faster next time, while T-cell response tends to last longer and so might offer longer-lasting protection.
The duration of antibody and T-cell responses is different for every vaccine and cannot be predicted accurately. It is also different for any natural infection, so the scientists have to wait and see how long our volunteers carry antibodies and T cells specific for Sars-CoV-2.
A Covid-19 vaccine developed by CanSino Biologics and China’s military research unit has also shown to be safe and induced immune response in most of the recipients, researchers said on Monday.
Meanwhile, Britain has signed deals to secure 90 million doses of two possible Covid-19 vaccines from the Pfizer and BioNTech alliance and French group Valneva.
It now means the UK has purchased close to 200 million doses – more than enough to immunise its total population, though two doses per person are likely to be required to boost protection. Additional reporting - The Guardian