He told the BBC there is “more than enough of the Pfizer or Moderna vaccine” for the 8.5mln residents aged between 18 and 29.
The UK has secured 40mln doses from Pfizer/BioNTech and 17mln from Moderna, which has started deliveries this week.
Distribution of the Pfizer vaccine has been underway for months.
Both J&J and Novavax are awaiting UK approval, with Novavax expected as early as this month.
Valneva, which will manufacture the UK supply at a plant in Scotland, is currently entering the final stage of trials after positive results earlier this week.
GSK and Sanofi experienced delays after announcing their candidate had shown no impact on the over-50s in December, so they have refined the formulation in the hope to make it available in the final quarter of 2021.
On Wednesday, the Medicines and Healthcare products Regulatory Agency (MHRA) imposed that under 30s without underlying issues making them vulnerable to the virus should be offered another vaccine.
The decision came after the authorities deemed blood clots a potential side effect, albeit extremely rare.
Up to March 31, thrombosis was reported in 79 people though over 20mln doses had been administered in the UK.
Meanwhile, a new study suggests there is a correlation between the fall in deaths and the vaccine rollout in the UK.
Findings from Imperial College London and Ipsos MORI also found that infections fell by 60% since February.
“his is hugely encouraging and shows we’re headed in the right direction,” said Professor Paul Elliott, director of the REACT programme from Imperial’s School of Public Health.
“However, in our most recent data there has been a flattening off in the infection rate with an R number now around one. This shows that we need to continue to approach the situation with caution and keep sticking to the rules.”
Shares in AstraZeneca rose 2% to 7,252p on Thursday afternoon.