Lockdown restrictions could be lifted from early March, with a return to the tier system for controlling Covid-19, the vaccines minister has said.

Nadhim Zahawi said that once millions of the most vulnerable are vaccinated with a first dose by the middle of February, it takes just a few weeks for their immune response to kick in and offer protection.

The Government is currently on track to vaccinate 15 million people across the UK by mid-February, including health and social care staff, the elderly and people in care homes.

Mr Zahawi told BBC Breakfast: “If we take the mid-February target, two weeks after that you get your protection pretty much for the Pfizer BioNTech (jab), three weeks for the Oxford AstraZeneca, (then) you are protected.

“That’s 80% of mortality. One of the things that we don’t know yet – and the deputy chief medical officer Jonathan Van Tam is on record as saying ‘look give me a couple of months and I’ll tell you’ – is the impact of the vaccine on transmission rates, ie infecting people.

“So, that will become apparent. So there are a number of caveats that, obviously, stand in the way of us reopening the economy.

“It will be gradual, it will be probably through the tiered system, but you’re looking at that sort of period – two to three weeks after the middle of February where we’ve protected those top four cohorts.”

Mr Zahawi then told Times Radio that by the “first or second week of March” there should be “very clear evidence of a sort of a break in the correlation between infection rates and hospitalisation and obviously death”.

He added: “But of course, there are a lot of unknowns, we don’t know the impact on transmission of the vaccines yet.

“There are lots of caveats on this so I don’t want to sort of over-promise and under-deliver on this.”

Asked if there was a role for mass testing, Mr Zahawi said the combination of vaccination and mass testing would allow the economy to gradually reopen.

And on the question of schools going back in early March, he said: “I’m saying to you that there are lots of uncertainties, we still don’t know what the impact of the vaccines are on transmission… but they are top of our list in terms of wanting them to reopen as soon as practically possible, with a combination of testing and, of course, vaccination as well.”