Every adult in the UK should have had the chance to have both doses of a coronavirus vaccine by mid-September, the Government said.
The gap between jabs is to be reduced from 12 weeks to eight for all under-40s, the Health Secretary said.
Sajid Javid told MPs the move amounted to “reinforcing our vaccine wall of defence further still”.
Giving a statement in the Commons on Monday, he said: “Today, even though cases are heading upwards in line with what we expected, hospitalisations are increasing at a much lower rate and deaths are at just 1% of the figure we saw at the peak.
“Our vaccines are building a wall of protection against hospitalisation, and jab by jab, brick by brick that wall is getting higher.”
Mr Javid said 86% of UK adults have had at least one jab and 64% have had two.
He added: “We are reinforcing our vaccine wall of defence further still. I can tell the House that we are reducing the dose interval for under-40s from 12 weeks to eight, which will mean that every adult should have had the chance to be double jabbed by mid-September.”
Meanwhile England’s chief medical officer Professor Chris Whitty said the Joint Committee on Vaccination and Immunisation (JCVI) is “rightly taking time” to consider all the data before making a final decision on whether or not to advise that children should be jabbed.
He said: “For any vaccine, what you want to be confident of is that the benefits of the vaccine outweigh any risks of the vaccine for the children involved.”
Due to the fact children are generally less badly affected by Covid, Prof Whitty said there would need to be “even greater confidence about the safety because the risk benefit is potentially therefore going to be more marginal”.
He said: “What we’re really trying to work out at this point in time is the relative protection that the vaccines provide for children. But I think we’re very confident that vaccines would protect children to a high degree.”
Earlier on Monday, the Prime Minister’s official spokesman told Westminster reporters the Government is still waiting on advice from the JCVI regarding jabs for children.