Kate Bingham said officials hope to give the vaccine to around 30 million adults - less than half of the country's population of 67 million.
The head of the immunisation programme told the Financial Times: "People keep talking about 'time to vaccinate the whole population' but that is misguided.
"There is going to be no vaccination of people under 18.
"It's an adult-only vaccine for people over 50 focusing on health workers and care home workers and the vulnerable."
In September, the government's Joint Committee On Vaccination And Immunisation published a draft list showing who is likely to be at the front of the queue for a jab if or when a coronavirus vaccine is approved in the UK.
The committee said a "simple age-based programme" was recommended as a means of deciding who gets priority, adding that this approach "will likely result in faster delivery and better uptake in those at the highest risk".
The draft list named older adults in care homes and care home workers as the first group, followed by those aged over 80, over 75, over 70 and over 65.
The first group of younger adults - those under the age of 65 with conditions that leave them at high risk of developing serious complications from the virus - would be in the sixth priority group. They would be followed by those aged under 65 who have a moderate risk level.
The rest of the population is listed as a group at number 11, after other older groups over the age of 50.
Earlier on Sunday, Health Secretary Matt Hancock said he supports the prioritisation list, saying: "We've got to get the vaccine to the people who are most likely to be badly affected by coronavirus first.
"But it is also important because people can know in advance that there is a prioritisation and we will reach people when it is clinically right to do that.
"And then there's a huge logistical operation which we're planning, led by the NHS with the support of the armed services to make sure we have the logistics in place to get this rolled out as fast as it is feasibly possible."
A government spokesperson said: "We want as many people as possible to access a COVID-19 vaccine and we are considering the advice of the independent Joint Committee for Vaccination and Immunisation on which groups of people to prioritise.
"The committee's interim advice is the vaccine should first be given to care home residents and staff, followed by people over 80 and health and social care workers, then to the rest of the population in order of age and risk.
"An enormous amount of planning and preparation has taken place across government to quickly roll out a safe and effective vaccine."