In research published on Monday in the journal Lancet, scientists said the vaccine produced a dual immune response in people aged 18 to 55 – provoking a T-cell response within 14 days of vaccination and an antibody response after 28 days.
More trials will need to be conducted to establish how long these cells last for within the body. It is also unclear whether the vaccine can prevent people from falling ill or lessen the symptoms of Covid-19.
AstraZeneca has said it hopes to deliver and start distributing Oxford University’s Covid-19 vaccine by the end of the year, after preliminary trial results revealed it induces a strong immune response within humans and appears to be safe.
Professor Sarah Gilbert, co-author of the study, described the findings as promising but said there “is still much work to be done before we can confirm if our vaccine will help manage the Covid-19 pandemic”.
Oxford University has partnered with AstraZeneca to produce the vaccine globally, with the pharmaceutical giant already committed to making 2 billion doses.
In light of Monday’s announcement, CEO Pascal Soriot said the company was hopeful that the vaccine would be ready for distribution by the end of the year.
“The question of when we’ll be able to distribute is a function of mostly, in fact, the infection rate in the community – therefore how quickly we can show efficacy,” he said.
“And then it will be in the hands of the regulators to review the data in their various geographies.
“Our hope is that we can actually start delivering the vaccine before the end of the year, and how early before the end of the year depends really on infection rates in the community.”
Mr Soriot said that AstraZeneca, which has struck deals with the UK, France, Germany and the US to deliver supplies of the vaccine, would begin the manufacturing process in parallel to running the next stages of the ongoing study.
“The only way to be ready to distribute the vaccine shortly after we get the results is to manufacture in parallel to doing the clinical development,” he said.
Phase two and three trials evaluating the vaccine’s effectiveness have been expanded beyond the UK to South Africa, Brazil and the US, where infections rates are still high, to allow researchers to assess whether it can block or limit transmission among large populations.
The study’s authors have also noted that more research is needed to confirm the findings in different groups of people – including older age groups, those with other health conditions, and in ethnically and geographically diverse populations.
Mr Soriot said results on the vaccine, in terms of its effectiveness and the longevity of the immune response it induces, are meanwhile expected to be available between September and November.
He added that there were a number of factors which would influence the results gathering, particularly the infection rate in a community.
“When a country like the UK manages the infection rate, it’s very good news of course, but in the context of getting to an answer for clinical trials and vaccines it’s not good news because it sort of delays the outcome,” he said.
“We’re working as quickly as we can but of course there are things that we cannot control, in particular the infection rate in the community which influences the results.
“We will be able to deliver results in September, but it may take another month or two.
“We need several vaccines, as you see here we need two doses, other vaccines will need two doses. If we want to vaccinate lots of people (we) will need several vaccines.”
Scientists and medical researchers across the UK have meanwhile welcomed the “very encouraging” results from Oxford University and AstraZeneca.
The speed at which the trial has been conducted has also been praised, with the preliminary results suggesting the vaccine is safe and causes few side effects.
Professor Fiona Watt, executive chairwoman of the Medical Research Council, which helped to fund the trial, said: “It is truly remarkable how fast this vaccine has progressed, with our support, through early clinical trials, and it is very encouraging that it shows no safety concerns and evokes strong immune responses.
“There is a lot that we don’t yet know about immunity to the virus that causes Covid-19.
“However, it seems that both antibody and T cell immunity are important, and this vaccine triggers both responses.
“The much anticipated next milestone will be the results of the larger trials that are happening now to find out if the vaccine will protect people from the virus.”