The government cannot guarantee that the current lockdown in England will be the last, a minister has said.

The Foreign Office minister James Cleverly said it was impossible to give the public certainty because “viruses don’t work like that”. He told Sky News on Friday: “We do want it to be the last lockdown, that’s what we’re working towards.”

Lockdown restrictions and the rapid vaccine rollout were having an impact, Cleverly said, but “no one can predict with complete certainty” what the virus will do and how it will evolve.

“We are taking the right action, we are doing the right things and we very much hope that this will be the last lockdown. We can’t give complete 100% certainty because viruses don’t work like that,” he said.

Research suggests coronavirus infections in England have fallen by two-thirds since January, but levels remain high and it is still unclear the extent to which far falling rates are the result of the vaccine rollout or the ongoing lockdown restrictions.

Boris Johnson is expected to set out his roadmap for easing measures in England on Monday. The plan could include the earliest possible dates for reopening different sectors of the economy and pupils could start returning to classrooms from 8 March.

The prime minister said at the daily press conference earlier this week that the plan would be based “firmly on a cautious and prudent approach” to ensure that coming out of this lockdown would be irreversible. He also stressed that any easing of measures could be pushed back if the situation were to change.

Speaking on BBC Radio 4’s Today programme, Prof Neil Ferguson from Imperial College London and a senior scientific adviser, said the “downside of taking bigger risks is you risk having to lock down again, which is even more disruptive economically and socially”. He was encouraged by the government’s cautious approach, he said, and expected to see an incremental approach, “namely relax one thing and see what the impact is, relax again”.

“It still may well be that by the end of May, we’re in a very different country than we are today,” he said. He cautioned, however, that this depended on things panning out as hoped and as the current data suggested they would. “There are threats out there, we don’t know for instance quite how effective the vaccines are, how long immunity will last, there is the threat of variants,” he said. “So we have to be driven by the data and the trends we see.”

In a later interview with BBC Breakfast, Cleverly said the government wanted to open up society and the economy, but only on the condition that it were safe to do so. Asked whether Britons would be allowed to go on summer holidays this year, he said it would be wrong for him to speculate at this stage.

“I get how frustrating this is, it’s completely natural. We all want to get a break from this, I get that. But it would wrong for me to start speculating now,” he said. “We are assessing the numbers, we are making a judgment based on the science and we will be making an announcement on Monday. I can’t go further than that.”