More than 1m additional patients across England will be contacted and invited to book a jab - with 37-year-olds to receive text message invites on 18 May, and 36-year-olds the following day.
The expansion of the COVID-19 vaccine rollout comes as the European Medicines Agency updated advice on storage of the Pfizer/BioNTech vaccine.
The change approved for EU member states 'extends the approved storage period of the unopened thawed vial at 2-8°C (i.e. in a normal fridge after taking out of deep-freeze conditions) from five days to one month'.
If approved for the UK, the extended storage period could prove a major boost for vaccination sites as they work through patients aged under 40 - for whom the Moderna and Pfizer/BioNTech vaccines are preferred to the Oxford/AstraZeneca jab.
More than 930,000 appointments for COVID-19 jabs have been made in less than a week since the vaccination programme opened to 38- and 39-year-olds, NHS England has said.
A total of 36.7m people had received a first dose of vaccine UK-wide by 16 May - around 70% of the adult population. Nearly two in five adults UK-wide have now received both doses of vaccine.
NHS national medical director Professor Stephen Powis, said: 'Bookings for the fastest and most successful NHS vaccination programme in history continue to surge with more than 930,000 appointments made in a matter of days since opening up to 38- and 39-year-olds.
'With well over 30m first doses of vital protection against coronavirus delivered just six months into the NHS vaccination drive, the NHS is able to open up to 36- and 37-year-olds as the programme continues at pace.'
The expansion of the COVID-19 vaccine campaign in England comes after officials confirmed patients aged over 50 would be offered their second dose four weeks earlier than planned to help prevent the spread of the so-called Indian variant of the virus, B.1.617.2.
NHS England’s lead for the NHS vaccination programme Dr Emily Lawson said: 'Well over 47m vaccinations have been delivered in England since the world’s first jab in December and thanks to the NHS’ incredible efforts we are seeing vaccinations demonstrably reducing the need for hospital care as well as saving thousands of lives from coronavirus.'