Boris Johnson said the latest data shows that vaccines are effective against the Indian variant, with hopes growing for June 21 unlocking to remain on track.
At Prime Minister's Questions, Mr Johnson said the latest data indicates the jabs are working against all variants of the virus.
The spread of the B1617.2 variant had cast doubt on next month's plans to ease the remaining restrictions in England, but Mr Johnson has said there is no conclusive evidence to suggest a deviation from the road map.
In a further sign of optimism, the Prime Minister told MPs on Wednesday: "We've looked at the data again this morning and I can tell the House we have increasing confidence that vaccines are effective against all variants, including the Indian variant."
Mr Johnson thanked people in Bolton and Blackburn - Indian variant hotspots - for "coming forward in record numbers" to receive a jab.
The Prime Minister's official spokesman said later that Mr Johnson had been referring to data on daily case rates as well as to studies published in the UK and elsewhere which showed "high levels of efficacy" for the vaccines against the virus.
He stressed however that ministers would want to see more information before making decisions on the next steps toward lifting lockdown.
The spokesman said: "We have regular data that is published daily that tracks through right down to a very granular level on things like case rates.
"That is the information that the Prime Minister is seeing. Currently in that data we are not seeing any sharp increases or significant areas of concern.
"Clearly it is important to stress that we want to give more time to get more data in so we can make decisions on our approach on the next step."
