As part of a vastly accelerated logistics operation, doses of various candidate vaccines are already being manufactured, even before the results of final studies have been submitted for approval by regulators.
Stephen Evans, a professor at the London School of Hygiene and Tropical Medicine, said scientists wanted to see the findings "before concluding that the responses were similar" between the older and younger age groups.
The AstraZeneca/Oxford vaccine is one of the most promising and advanced in the world to combat the global pandemic, which has now claimed the lives of 1.1 million people.
The results have been derived from immunogenicity tests conducted between the months of July and August in a varied group of volunteers, including younger and older adults.
But should a vaccine become available, many people in Ireland say they will not take it. 19% of those aged between 25 and 34 and 18% of those aged between 18 and 24 said they would not take a Covid-19 vaccine, according to a new poll carried out by Ipsos-MRBI for the IPHA.
An AstraZeneca spokesman said the initial results "further build the body of evidence for the safety and immunogenicity" of its experimental vaccine.
With dozens of vaccine candidates in late-stage clinical trials, including AstraZeneca's, hope remains that a safe, effective vaccine will be developed before the end of the year.
Asked if some people could receive a vaccine this year, he told the BBC: "I don't rule that out but that is not my central expectation".
The vaccine most waited for the people across the globe is in news for two unfortunate incidents.
Patel declined to comment on whether he thought 500 billion rupees would suffice, but said he wasn't anxious about potential delivery and cold-chain storage bottlenecks given that vaccine supply will initially be restricted to priority areas and those at high risk.
AstraZeneca said the reactogenicity - the common, expected side-effects - were lower in older adults. A late-stage trial of the shot was restarted last week in the US after a temporary halt that followed a participant's illness in a separate United Kingdom study.
Russian state-backed researchers have developed two other Covid-19 vaccines, which are undergoing various stages of government approval and clinical trials.
The first coronavirus vaccine could be here "within weeks" and Ireland could be among the first countries to receive batches.