The final step out of lockdown in England is set for 21 June, when the government will remove “all legal limits on social contact” – although some social distancing and mask-wearing rules will remain.

However, a senior government minister has said that it is too early to speculate about whether this will go ahead as planned, amid concern about increasing cases of the Delta variant, first detected in India and known as B.1.617.2.

The Guardian spoke to a number of experts about whether the planned 21 June lockdown lifting should be delayed – and if so, why.

John Bell, immunologist

John Bell, regius chair of medicine at the University of Oxford, said that he had looked at the numbers on Tuesday and that he was not concerned with hospitalisations, which are “pretty flat”, or mortality, which is “very flat”.

He puts this down to the rapid rate of vaccinations, saying that the most “important thing is that among those who would get sick and die from the virus, around 80-90% of people are now vaccinated”.

He said that vaccines would, undoubtedly, prevent hospitalisations and deaths. He says trying to get rid of the virus entirely from the UK is “foolish” and will “never happen”.

“If, on the other hand, you are trying to manage the disease and are aware of the fact there will be other variants and a certain amount of disease activity in the background but low hospitalisation and deaths, then that is another question. You need different strategies for the two approaches,” he said.

“I think we have to watch the figures and at the moment I don’t see anything that makes me anxious, there are more cases but not that many.”

Susan Michie, behavioural scientist

Susan Michie, professor of health psychology and director of the centre for behaviour change at UCL, said that she wished there had been more focus on “data” and not “dates”.

“But the emphasis has been on dates rather than data, and it would have been good if this was not the case,” she said.

She added that what was happening now was similar to the spread of the Alpha variant, first detected in Kent and known as B.1.1.7, in terms of increasing transmission, adding that “we should be concerned”.

“We all suffered the consequences of not acting soon enough with another lockdown,” she said. “No one wants that to happen again so the starting point in communication should be focusing on preventing another wave. The key thing is to learn from the past and the mistakes we made and one thing we learned about the virus is that you cannot wait until you are certain of another wave. You have to act when there is the possibility of it or you lose control over the virus rising exponentially.”

Michie added that an increasing number of epidemiologists and public health experts, who had knowledge about the pandemic, were saying it would be extremely unwise to lift more restrictions.

Fiona Donald, consultant anaesthetist

President-elect of the Royal College of Anaesthetists, Fiona Donald, said that her views on the easing of restrictions came from the viewpoint of the millions of patients on waiting lists for operations. She worries that if restrictions are lifted too soon, hospitals will struggle once more – and there is already a huge backlog of people waiting for non-Covid related surgery.

“If hospitals get busy or even overwhelmed by Covid cases then they are unlikely to get surgery in a timely fashion and that is my main concern really,” she said.

Donald added that we should be guided by what “the science shows” and “there is a timeframe for that”, but whatever decision should be made on the basis that “the NHS can cope”.

She said it was “not just about hospitals filling up” but also when there were lots of infected patients in hospital “you use up disproportionate amounts of space and personnel and resources”.

Kate Nicholls, chief executive of UK Hospitality

Kate Nicholls, whose organisation represents pubs, restaurants, bars and clubs across the country, said the government delaying its roadmap for easing Covid restrictions in England would be hugely damaging for the industry.

“It’s critical we move ahead to step four of the roadmap. We’ve still got a quarter of premises that can’t open at all. Those that can open are trading under such severe restrictions they’re not profitable. Leaving restrictions in place is not viable. Every day restrictions are in place businesses are losing money and jobs are in jeopardy.”

Any delay would require the chancellor, Rishi Sunak, to bring forward a package of fresh economic support measures to prevent a fresh wave of job losses, she said. More than 3m jobs were furloughed at the start of May, according to the latest official figures, with almost half of staff in the hospitality sector receiving emergency wage support.

“The support is critical. For those businesses that can’t open yet it’s been 16 months without revenue at all. Particularly nightclubs, music venues, wedding venues and the events business that support them, those businesses are clinging on by their fingertips,” Nicholls said.

She said any reintroduction of tougher controls would be devastating for hospitality firms. “It would be a catastrophic, retrograde step. Businesses would close their doors for good almost immediately.”

“We see no reason why there should be a delay. There is nothing coming out in the epidemiological research or case numbers to suggest the roadmap is not on track.”

Jagjit Chadha, director of the National Institute of Economic and Social Research

Jagjit Chadha said there would be costs from delaying, but that the economic fallout would be much less than during previous lockdowns.

“The good news is that it looks like the economy has shown more resilience in the face of every successive lockdown. We’ve kind of learned how to deal with them,” he said. Britain’s economy shrank by about a quarter during the first lockdown from March 2020. However, GDP fell by about 10% in the second lockdown last autumn and by less than 5% at the start of this year during the third, he said. “The direct economic cost of lockdown seems to be less.”

Chadha said there was a strong case for delaying reopening because the economy had adapted over the past year, and that containing the virus was key for the country’s long-term economic recovery.

“So it’s got to depend on the growth of the infections and the virus. We should not stop ourselves from doing these things because of the impact on the economy. It’s a secondary question,” he said.

Research by the International Monetary Fund shows the economic impact from lockdown is about equal to the effects from people voluntarily social distancing when worried about higher rates of infection. This could strengthen the argument for keeping some restrictions in place, he said.

“People are so aware now of the infection and where it’s hitting. If we didn’t control it, you would see a reduction in expenditure in any case, as people won’t go out. Getting the virus under control is also the only way you can get back to normality on the economy.”