London: COVID-19 vaccine being developed by British-Swedish pharmaceutical firm AstraZeneca and Oxford University produced a strong immune response in older adults, raising hopes that it can protect the age groups most at risk from the virus.

The study, published in The Lancet medical journal, suggest that those aged over 70 - who are at higher risk of serious illness and death from COVID-19 - could build robust immunity to the novel Coronavirus.

"We were pleased to see that our vaccine was not only well-tolerated in older adults, but also stimulated similar immune responses to those seen in younger volunteers," Dr Maheshi Ramasamy, an investigator at the Oxford Vaccine Group, was quoted as saying to the BBC.

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"The next step will be to see if this translates into protection from the disease itself," Ramasamy added.

According to the researchers, two weeks after the second dose, more than 99 per cent of participants had neutralising antibody responses. These included people of all ages.

The T-cell response - another measure of how well the immune system responds - peaked two weeks after the first dose of the vaccine, regardless of age.

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"The robust antibody and T-cell responses were seen in older people in our study are encouraging. The populations at greatest risk of serious COVID-19 disease include people with existing health conditions and older adults," Ramasamy said.

"We hope that this means our vaccine will help to protect some of the most vulnerable people in society, but further research will be needed before we can be sure," she added.

According to the study, older adults were also less likely to experience side-effects, which were usually mild. And there were no serious safety issues relating to the vaccine, called ChAdOx1 nCov-2019.

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Three vaccines - Pfizer-BioNTech, Sputnik and Moderna -- have already reported good preliminary data from phase three trials, with one suggesting 94 per cent of over-65s could be protected from COVID-19.

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