A vaccine developed at Oxford University has triggered a strong immune response in older adults.
Latest trial results show a robust response in healthy adults, aged 56 to 69, as well as people over 70.
Phase two data, published in The Lancet, suggests one of the groups most vulnerable to serious illness and death from the virus could build immunity, researchers have said.
According to the researchers, volunteers in the trial demonstrated similar immune responses across all three age groups (18-55, 56-69, and 70 and over).
The study of 560 healthy adults – including 240 over the age of 70 – found the vaccine is better tolerated in older people compared with younger adults.
Volunteers received two doses of the vaccine candidate, or a placebo meningitis vaccine.
No serious adverse health events related to the vaccine were seen in the participants.
The results are consistent with phase one data reported for healthy adults aged 18-55 earlier this year.
Dr Maheshi Ramasamy, investigator at the Oxford Vaccine Group, said: “Older adults are a priority group for Covid-19 vaccination, because they are at increased risk of severe disease, but we know that they tend to have poorer vaccine responses.
“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.
“The next step will be to see if this translates into protection from the disease itself.”
Researchers have said their findings are promising as they show that the older people are showing a similar immune response to younger adults.
Dr Ramasamy added: “The robust antibody and T-cell responses 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.
“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.”
The study also found the vaccine, being developed with AstraZeneca, was less likely to cause local reactions at the injection site and symptoms on the day of vaccination in older adults than in the younger group.
Adverse reactions were mild – injection-site pain and tenderness, fatigue, headache, feverishness and muscle pain – but more common than seen with the control vaccine.
Thirteen serious adverse events occurred in the six months since the first dose was given, none of which were related to either study vaccine.
UK authorities have placed orders for 100 million doses of the vaccine – enough to vaccinate most of the population – should it receive regulatory approval.
The Oxford findings come after Pfizer and BioNTech announced that their vaccine candidate has shown 95% efficacy, with a 94% effectiveness in those aged 65 and over.
Forty million doses of that vaccine have been bought by the UK, with rollout potentially starting in early December if the jab is given the green light by regulators.
Earlier in the week US biotech firm Moderna released data suggesting its vaccine is almost almost 95% effective.