During a press briefing at Downing Street on Monday, Mr Johnson said the gap between doses would be reduced with the aim of ensuring everyone aged over 18 was 'double jabbed by the middle of September'.
Until now the recommendation for an eight-week gap only applied to those aged 40 and over. Mr Johnson also confirmed that a booster vaccination programme for those most vulnerable to COVID-19 would begin in September. NHS England is due to set out how the booster programme will work by the middle of July.
The prime minister made the announcement while setting out how the government plans to ease restrictions in England when it moves to step 4 of its roadmap, currently due to take place on 19 July. The final decision on whether to proceed to step 4 will be taken next Monday (12 July).
Rules on face coverings
Mr Johnson revealed that if the move goes ahead the government intends to roll back almost all legal restrictions aimed at curbing the spread of COVID-19 to 'allow people to make their own informed decisions about how to manage the virus'.
People will no longer be required to wear a face covering in any setting, which looks set to also apply in healthcare settings including GP practices. Instead guidance would 'suggest' situations where people might choose to wear a face covering, such as in crowded indoor places or in parts of the country where cases were rising.
The government also plans to end rules on social distancing, scrap legal limits on gatherings and the advice to work from home will end.
People will still be required to self isolate if they test positive for COVID-19 or are contacted by NHS Test and Trace and told they need to isolate. However, it is expected that the need to isolate will be lifted for people who have been double vaccinated and also for children in the near future.
The prime miniser admitted that cases of COVID-19 were rising rapidly and they could reach 50,000 a day by 19 July. He said that hospitalisations were also rising, adding 'we must reconcile ourselves to more deaths from COVID'.
Mr Johnson said that the only reason the government was able to consider moving to step 4 of the roadmap was because of high levels of vaccination in the adult population and the ongoing effectiveness of the vaccination programme.
England's chief scientific officer Sir Patrick Vallance told the briefing that the link between COVID-19 cases and hospital admissions and deaths had been 'weakened but not broken' as a result of widespread vaccination.
He said he expected both admissions and deaths to continue to rise in the coming weeks, although not at the same rate as they had done earlier this year. However he did warn that hospitalisations were 'rising quite steeply in some places'.
England's CMO Professor Chris Whitty said modelling suggested that the peak of hospital admissions in this wave of the pandemic would be lower than the NHS had seen in January, but he added that there was 'some degree of uncertainty' about this. He said the country was at the point where the 'epidemic is clearly significant and rising'.
Mr Johnson said that if the government did not relax remaining restrictions in the summer when there was a natural 'firebreak' provided by the school holidays 'when will we be able return to normal?'
'To those who say we should delay again, the alternative to that is to open up in winter when the virus will have an advantage or not at all this year,' the prime minister added.
Ahead of the briefing doctors' leaders warned the government against removing COVID-19 restrictions too quickly. The BMA urged the government to keep some ‘targeted measures’ to control the spread of the virus, including requiring people to wear face coverings in enclosed public spaces, such as healthcare settings, public transport and shops.