The vaccine triggers protective antibodies and T-cells in older age groups, the FT said, citing two people familiar with the finding, encouraging researchers as they seek evidence that it will spare those in later life from serious illness or death from the virus.
Details of the finding are expected to be published shortly in a clinical journal, the FT said, without naming the publication.
The findings echo data released in July which showed the vaccine generated "robust immune responses" in a group of healthy adults aged between 18 and 55, the newspaper reported, citing people aware of the results from so-called immunogenicity blood tests.
But the FT cautioned that positive immunogenicity tests do not guarantee that the vaccine will ultimately prove safe and effective in older people.
AstraZeneca, which is developing the vaccine with Oxford University researchers, is seen as a frontrunner in the race to produce a vaccine to protect against COVID-19.
Oxford and AstraZeneca did not immediately respond to Reuters' request for comments.
One of the world's leading coronavirus vaccine candidates, called AZD1222 or ChAdOx1 nCoV-19, was developed by Oxford University scientists and licensed to AstraZeneca in April, which took on the task of scaling trials and production.
AstraZeneca resumed the US trial of the experimental vaccine after approval by U.S. regulators, the company said on Friday.
It is a viral vector vaccine that uses a weakened version of a chimpanzee common cold virus that encodes instructions for making proteins from the novel coronavirus to build immunity against COVID-19.