It is "too early" to say if people will be allowed to take summer holidays abroad or in the UK, Boris Johnson has said.
The prime minister stopped going as far as his transport secretary, who said this morning "people shouldn't be booking holidays right now - not domestically or internationally".
Grant Shapps' comments had prompted fury from Charles Walker, a senior Tory MP who told Sky News it was a "stupid thing to say".
Mr Johnson tried to skirt round the subject at a No 10 coronavirus briefing on Wednesday, saying: " I'm afraid it is just too early for people to be certain about what we'll be able to do this summer."
More details will be announced in the week beginning 22 February as part of the promised roadmap out of lockdown, Mr Johnson vowed.
He added: "I understand why people want to make plans now, but we're just going to have to be a bit more patient."
Mr Johnson also did not deny the government was working on developing an app for people to show when travelling internationally, containing details about their COVID-19 status.
We're looking at all sorts of things that we may wish to do in the months ahead, he said.
The idea of immunity passports has been floated for several months, with Sky News confirming last Friday that ministers are looking into the creation of a digital vaccine document.
Research groups are said to have been set up on the subject as attention turns to what will happen once jabs are more widely rolled out across the world.
Tory MP Simon Clarke said the "bottom line" is that "travel abroad this year is unlikely".
"Holidays within the UK are likely by the summer, but the government can't make a hard and fast statement to this effect at this stage," he tweeted.
"If you book (as I have), you do so at your own risk."
It comes as the number of people to get a first COVID-19 jab passed 13 million - proof, Mr Johnson said, that the government is on track to offer a jab to everyone in the top four priority groups by 15 February.
He repeated a call for anyone in those groups who has not been offered a vaccine yet to book one with the NHS directly.
The prime minister also cautioned that while cases, deaths and hospitalisations are down, with his "layman's eye" he could not yet see results "directly attributable to the vaccine".
Sir Patrick Vallance, the UK government's chief scientific adviser, said that was "not surprising" because it takes time for immunity to build up - so there should start to be a noticeable difference "within the next couple of weeks".