There is “early data” showing a reduction in transmission in people who have had a coronavirus vaccine, the health secretary has said.
Matt Hancock said hospital admissions were falling “much more sharply” than they were in the pandemic’s first wave.
The government aims to offer a first jab to all adults in the UK by the end of July, with one in three adults already vaccinated, Mr Hancock said.
The PM will unveil his road map for ending England’s lockdown on Monday.
As part of the plan, Public Health England will publish new data new data on the impact of vaccines on transmission rates.
Mr Hancock told the BBC’s Andrew Marr show that he was “absolutely delighted” with the progress of the vaccine rollout.
But he added that while hospital admissions were falling, the level was still “far too high”.
The health secretary reiterated the government’s new plan to offer a jab to adults aged 50 and over and those in the top nine priority groups by 15 April, followed by all adults by the end of July.
He said the “success” of the vaccine rollout so far had allowed them to accelerate it, a move he added would have “an impact” on how quickly society would be able to return to normal.
Revealing that one in three adults had already received a jab, he said ministers were “confident” the vaccine worked effectively against the old strain of the virus and the so-called Kent variant.
However, he warned the government did “not yet have the confidence” the jab was “as effective” against the South Africa variant and the variant first seen in Brazil, but that enhanced contact tracing and stricter border controls were reducing the cases of those variants in the UK.
The latest data showed “around a dozen” new cases of the South African variant in the UK, with an overall total of around 300 cases, Mr Hancock added.
Asked if the spread of the South Africa variant was “shrinking”, he said: “I think that’s a good summary yes”.
Meanwhile, Prof Peter Openshaw, a member of the New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), told BBC Radio 4’s Broadcasting House programme that vaccine transmission data was “looking really good”, but scientists still needed to estimate by how much the vaccine interrupted transmission.