Those 40 to 49 are being told they are next on the list to get their Covid-19 vaccination as The Joint Committee on Vaccination and Immunisation provided at update during at Downing Street briefing.
During a briefing, the JCVI started the Downing Street briefing by saying phase one of the programme was aimed at preventing severe mortality from coronavirus.
Dr Marie Ramsey said older age groups were priorities as well as those with underlying health conditions.
She said there was evidence the vaccine is having an impact.
"One dose of Pfizer reduces risk of symptomatic cases in older people", she said.
The AstraZeneca vaccine is also said to be performing well.
Dr Marie Ramsey said there are now signs of death and hospital admissions declining at a faster rate than the younger population.
Phase two is now ready to be thought about.
Professor Wei Shen Lim said phase one involved all adults aged 50 and over and adults 16 and over with underlying health conditions.
Phase will be offered to those aged 50 and younger.
JCVI say they have considered various strategies, first to offer vaccines to protect those at risk of serious disease, second to reduce transmission with the population and third to structure a programme according to occupation risk.
'Age is the predominant factor'
This means that in phase 2, priority will be given in the following order: