London: An experimental coronavirus vaccine being developed by AstraZeneca and Oxford university was safe and produced an immune response in early-stage clinical trials, data showed on Monday, keeping alive the hope it could be in use by the end of the year.
The vaccine, called AZD1222, has been described by the World Health Organization's chief scientist as the leading candidate in a global race to halt a pandemic that has claimed more than 600,000 lives.
More than 150 possible vaccines are in various stages of development with US drugmaker Pfizer and China's CanSino Biologics also reporting positive responses for their candidates on Monday.
The vaccine from AstraZeneca and Britain's University of Oxford did not prompt any serious side effects and elicited antibody and T-cell immune responses, according to trial results published in The Lancet medical journal, with the strongest response seen in people who received two doses.
UK Prime Minister Boris Johnson, whose government has helped to fund the project, hailed the results as "very positive news."
However, the researchers cautioned the project was still at an early stage.
"There is still much work to be done before we can confirm if our vaccine will help manage the COVID-19 pandemic," vaccine developer Sarah Gilbert said.
"We still do not know how strong an immune response we need to provoke to effectively protect against SARS-CoV-2 infection," she said, adding researchers needed to learn more about COVID-19 and continue late stage trials which have already commenced.
AstraZeneca shares surged 10%, but then gave up most of those gains, to trade 1.2% stronger on the day.
AstraZeneca has signed agreements with governments around the world to supply the vaccine should it prove effective and gain regulatory approval. The company has said it will not seek to profit from the vaccine during the pandemic.
Adrian Hill, the director of Oxford university's Jenner Institute, said early projections that a million doses of the vaccine could be made by September could be an under-estimate, depending on how quickly late-stage trials can be completed.
He added it remained possible that the vaccine could be in use by the end of the year.
Researchers said the vaccine caused minor side effects more frequently than a control group, but some of these could be reduced by taking paracetamol.
AZD1222 was developed by Oxford university and licensed to AstraZeneca, which has put it into large-scale, late-stage trials to test its efficacy. It has also already signed deals to produce and supply over 2 billion doses of the shot.
The new trial included 1,077 healthy adults aged 18-55 years with no history of COVID-19.
WHO official hails 'good news' from early trials
The head of emergencies at the World Health Organization is hailing good news in results shown by two COVID-19 vaccine candidates in early trials, but warns there's a long way to go.
"We now need to move into larger-scale real-world trials," Dr Michael Ryan told reporters at a news conference in Geneva.
"But it is good to see more data and more products moving into this very important phase of vaccine discovery."
Ryan noted there are 23 COVID-19 candidate vaccines in clinical development, but until Monday only one had produced Phase 1 clinical data.
(With inputs from Reuters and AP)