An early stage of testing – a combined phase 1 and 2 trial – strongly suggested that the Oxford/AstraZeneca vaccine would offer protection to older people. It showed the vaccine generated just as strong an immune response in older participants as younger ones.
However, as we don’t know to what extent different parts of the immune response act against the virus, this alone didn’t prove that the vaccine would be effective in this age group. And in the final phase of testing – phase 3 trials – which are designed to prove that a vaccine is protective, there weren’t enough people over 55 to give a reliable estimate of protection for this group.
Exactly how protective the vaccine is in older people remains uncertain. But a recent preprint suggests it works very well. A single shot of the Oxford/AstraZeneca vaccine appears to reduce the chances of people being admitted to hospital with COVID-19 by 80% after the first dose.