More than 150 armed personnel and dozens of government forestry officials were deployed to capture the wolves last month
"We are now initiating studies to evaluate how well the vaccine induces immune responses in older adults, and to test whether it can provide protection in the wider population."
However, Pollard told BBC radio it was "not possible to predict" when the potential vaccine might be ready for the wider population.
"It is a very difficult question to know exactly when we will have proof that the vaccine works," he said.
Much depended on having enough people who had been exposed to COVID-19 in the trial's next phase, he added.
The university and pharma giant AstraZeneca have signed a deal which could see up to 30 million of 100 million doses for the UK market available by September.
Oxford's effort involves its multidisciplinary Vaccine Group, set up in 1994 to study new and improved inoculations, and the Jenner Institute, which works on both human and livestock diseases.
It is based on a chimpanzee adenovirus - a common cold virus - which has been genetically changed to stop Covid-19 replicating in humans.
The British government, which has given the endeavour around £85 million ($104 million, 95 million euros) in funding, has called it one of the "frontrunners" in the world's vaccine search.
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