The move follows the decision yesterday to open vaccination to those aged 44, after latest figures showed around two-thirds of people aged 45 to 49 had already received their jab.
The government has said that anyone who turns 42 before 1 July 2021 is now eligible to book an appointment for their first jab.
On Tuesday morning, health secretary Matt Hancock posted a video on Twitter announcing the extension of the vaccination programme.
He said: 'I am very excited to be able to tell you that today we are opening vaccination up to people aged 43 and 42, which includes me, so I'm really looking forward to getting my text.
'Yesterday we opened up to people aged 44 – that's gone very, very well. Thank you to the hundreds of thousands who have come forward and booked your appointment and now we're able to go that little bit further.'
He added: 'This vaccination roll out is going incredibly well, the uptake is astonishingly high.'
We are now inviting anyone aged 42 or over and those who will turn 42 before 1st July 2021 to book a COVID-19 vaccination.— Matt Hancock (@MattHancock) April 27, 2021
Thank you to everyone who has contributed to our national effort.
When you get the call, get the jab. pic.twitter.com/OCxJNRTDKA
On Monday NHS England warned vaccination sites to prepare for an 'uplift in bookings' as an advertising campaign to promote jabs for under-50s began. NHS England said a further announcement on jabs for all over 40s was expected 'very shortly' as vaccine supply becomes available.
Nearly 11m doses of COVID-19 vaccine have been administered UK-wide up to 25 April – more than 440,000 per day on average. A total of 76% of jabs have been second doses this month so far – but more than 2.6m people have received a first dose of vaccine in April to date.
NHS England medical director Professor Stephen Powis said: 'Just two weeks after rolling out the vaccine to those aged 45 and over, we are now ready to invite those aged 42 and 43, as the largest vaccination programme in NHS history continues at speed.
'The rapid rollout of the NHS vaccination programme, the swiftest in Europe, hasn’t happened by accident – it is down to months of careful planning and sheer hard work by nurses, doctors and countless other staff supported by our volunteers.'