England will be entering “uncharted territory” in its wholesale scrapping of Covid lockdown rules and infection numbers could easily rise above 100,000 a day over the summer, the health secretary has said. With Labour demanding that the widely expected reopening on 19 July is balanced with mitigation measures, Sajid Javid defended the approach set out by Boris Johnson on Monday evening, but acknowledged considerable uncertainty. Notably, a week after saying there must be “no going back” from unlocking, Javid, who took over from Matt Hancock 10 days ago, told BBC Radio 4’s Today programme that some restrictions might have to be reimposed in the future. Asked if this might happen, he said: “I hope not, and that’s certainly not in our plan.” Adding that the reopening plans maintained some powers for local authorities to take action, Javid said it remained possible that new variants of Covid could emerge, potentially with resistance to current vaccines: “The one thing that no one can say for certain anywhere in the world is the future progression of the virus.” Asked about government projections that infection rates were likely to reach 50,000 a day by 19 July, Javid accepted it was “fair to say” that even this figure could double or more. The highest daily infection rate for the UK thus far recorded was just over 81,000, seen in late December. “Because this is uncharted territory for any country in the world, as you go further out, week by week, the projections are even less reliable,” he said. “As we ease and go into the summer, we expect them to rise. They could go as high as 100,000. We want to be very straightforward about this in what we can expect in terms of case numbers. But what matters more than anything is hospitalisation and death numbers.” Questioned about what this could mean for hospitalisation rates, currently at about 300 admissions a day, Javid said the government had “a number of models that we look at internally” about how this could progress, but declined to give any projections. Announcing the plans at a Downing Street press conference on Monday, Johnson warned the public against going “demob happy”, but said the time had come to lift virtually all rules, calling this a “move from a universal government diktat to relying on people’s personal responsibility”. The prime minister said: “We must be honest with ourselves that if we can’t reopen our society in the next few weeks, when we will be helped by the arrival of summer and by the school holidays, we must ask ourselves: when will we be able to return to normal?” Javid is due to address MPs on Tuesday lunchtime, when he is expected to announce an easing of self-isolation rules for people who have received two vaccination jabs who come into close contact with someone who tests positive. “What I can say is, it makes sense because of the vaccines and the way they are working that people that are double vaccinated are treated differently to people who are not. And that’s what I’ll be saying in parliament,” he told Today. Prof Neil Ferguson of Imperial College London, a government adviser, said the impact of the Covid vaccination programme meant the expected third wave “is going to look very different from the second wave”, when daily death rates were above 1,000 people. “At the peak of the second wave 50,000 cases would translate into something like 500 deaths, but that’s going to be much lower this time, more like 50 or so,” he told Today. “The challenge is, there’s still the potential of getting very large numbers of cases and so if we get very high numbers of cases a day, 150,000 or 200,000, it could still cause some pressure to the health system. This is a slight gamble, it’s a slight experiment at the moment, and I think it’s justifiable and I’m reasonably optimistic, but policy will have to remain flexible.” One key area of contention is the plan to make all mask use voluntary, although transport providers such as airlines and train companies might be able to mandate it as a condition of travel. Jonathan Ashworth, the shadow health secretary, said Labour wanted the economy to reopen “in a balanced way”, contrasting this with what he termed the planned “high-risk free-for-all”. He told Today: “Yes, we need to reopen more, but we would maintain some mitigating precautions. We would maintain mask wearing on public transport and in shops, we would give support to premises to properly ventilate and install air filtration systems. And we would pay people proper sick pay and isolation support.” He added: “We understand why we want to get our economy reopened, we need to get our economy reopened, but why on earth would you throw all caution to the wind?” Asked about his own future mask use, Javid told Today he would “carry a mask with me for the foreseeable future” and wear it in crowded and enclosed spaces. However, he said he would choose to not do so even if it was recommended if the space concerned was not crowded.