The world-leading Oxford vaccine is believed to have generated a promising effect in volunteers. It has provoked twin correct responses not only in antibodies, which work to neutralise the virus before it can damage cells but also in T-cells that target and destroy cells that are already infected. The first trial results are due to be published on Monday.
Meanwhile US firm Moderna announced that all 45 volunteers in its early phase trial had developed immune responses without serious side effects.
The positive news suggests a rollout this year could still be on the cards despite problems with gathering data in the UK.
The update came as Britain’s coronavirus death toll passed 45,000 after 85 new fatalities yesterday.
Some 538 more positive test results were returned, pushing the total number of cases to 291,911.
The Oxford CHADOX1 nCoV-19 vaccine is now in large-scale phase three trials, including in Brazil and South Africa where infection rates are higher than the UK.
These will assess whether it can protect against COVID-19 but developers have yet to release early phase one results which would show whether it is safe and induces an immune response.
The Lancet confirmed that a paper on the findings is due out on Monday.
ITV News political editor Robert Peston reported the results would show that while some vaccines trigger only an antibody response, the Oxford one appeared also to generate a T-cell response.
A source told him: “It is important to keep in mind is there are two dimensions to the immune response, antibodies and T-cells.
“Everybody is focused on antibodies but there is growing evidence suggesting that the T-cell response is important in the defence against coronavirus.”
Shares in drug firm AstraZeneca surged yesterday following the update.
The firm has partnered with researchers to mass produce the vaccine and will aim to provide 30 million doses for the UK by September, if it is proven to work.
Professor Sarah Gilbert, who leads the team at Oxford University which was visited by Prince William last month, recently told MPs on the Commons Science Committee that the vaccine was generating the correct response.
Her comments came after a study from the Karolinska Institute in Sweden suggested twice as many people had developed T-cell immunity compared with those who had antibodies to COVID-19.
Professor Gilbert said: “T-cell immunity is very important in immunity to viruses and it’s something that’s often overlooked because it’s rather difficult to measure.
“What we know is, with our vaccine, it’s very good at inducing T-cell responses as well as antibody responses. In the paper coming out of the Karolinska Institute actually a lot of the T-cell responses were to the spike protein, which is the protein that’s in our vaccine.
“And we would expect to get T-cell responses as well as antibody responses to this vaccine. Again, we’ve seen that with the MERS coronavirus vaccine.”
Professor Gilbert explained that if T-cells are also generated by the vaccine, a weaker antibody response may be sufficient to prevent infection.
She added: “Because you’ve got two components that are contributing to immunity, you may not need such a high level of antibodies to get full protection if you’ve also got a strong T-cell response which is adding to that protection.”
Meanwhile, US firm Moderna released its latest findings in the New England Journal of Medicine.
The company, based in Cambridge, Massachusetts, was one of the first to start human testing of a vaccine for the novel coronavirus on March 16, 66 days after the genetic sequence was released.
It said its jab, another frontrunner in the global race for a defence, was safe and no participants suffered any serious side effects.
The volunteers developed neutralising antibodies in their bloodstream at levels found to be comparable to those found in people who survived COVID-19.
Dr Lisa Jackson, who led the study, said: “This is an essential building block that is needed to move forward with the trials that could actually determine whether the vaccine does protect against infection.”
More than half of volunteers in the American study reported mild or moderate reactions such as fatigue, headache, chills, muscle aches or pain at the injection site.
But scientists said minor side effects were a “small price to pay” for protection against COVID-19.
Dr Anthony Fauci, the US government’s top infectious disease expert, said: “No matter how you slice this, this is good news.”
He added: “If your vaccine can induce a response comparable with natural infection, that’s a winner. That’s why we’re very pleased.”
More than 100 vaccines are in development across the globe and scientific research is advancing at an unprecedented pace.
But the World Health Organisation and Unicef warned progress in improving the uptake of general vaccines among children had been disrupted by COVID-19.
Meanwhile more than 75 countries including Britain have expressed an interest in joining the COVAX financing scheme, designed to ensure any coronavirus vaccine can be fairly distributed among poorer nations.
Dr Seth Berkley, the CEO of Gavi, the Vaccine Alliance, said: “COVAX is the only truly global solution.”
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