The latest data shows nearly 47million jabs have been administered in the UK with 12,897,123 of those second doses.
He tweeted: “I’m very excited to open up vaccination to 42-year-olds - standing by my phone awaiting my text...”
The national booking system has been extended for the second time in two days to allow more healthy adults in their 40s to book their jab.
Watch: Jab bookings open to those age 42 and over in England
People in England who are aged 42 and over, or those who will turn 42 before July 1, can now arrange their vaccine appointment through the national booking website.
The system only opened to those aged 44 and over on Monday.
It comes as deaths involving Covid-19 in England and Wales have fallen 97 per cent since the peak of the second wave of the virus, new figures suggest.
Some age groups have recorded drops as high as 98 per cent or 99 per cent, as the combined impact of the lockdown and the vaccine rollout continues to drive down the number of infections and hospital admissions.
A total of 266 deaths occurred in the week ending April 9 where Covid-19 was recorded on the death certificate, according to the Office for National Statistics (ONS).
This is down 97 per cent from 8,965 deaths in the week to January 22, the peak of the second wave, when more than a thousand deaths were taking place each day.
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