UK ministers are considering delaying the end of Covid-19 restrictions by up to four weeks to allow more people to be fully inoculated.
Plans are being discussed for a two or four-week delay to the final easing measure on June 21, especially if the Indian variant leads to an increase in hospital admissions, The Times reported.
The more infectious strain now accounts for 91 per cent of all new cases in Britain.
Jim McManus, from the Association of Directors of Public Health, on Friday said “several pieces of data” about the rise of cases were concerning.
"Investing a bit of time is really important for enabling the vaccine programme to finish and do its job," he told the BBC's Radio 4 Today programme.
“That’s four weeks of keeping some of the stuff we have now, like social distancing, face masks and some other measures. We’re not talking about new restrictions and going backwards, we’re talking about going forwards but very slowly.”
Some scientists said a delay is not necessary because hospital admissions remained flat.
But Mr McManus said that allowing more community transmission was risky.
“I would counter that by saying if you get enough people infected you will get a rise in hospitalisations, you also get a significant rise in long Covid, which is something we want to avoid too,” he said.
"The second thing is the more people infected the more variants will develop and the more risk a variant will develop that evades the vaccine completely."
Prime Minister Boris Johnson will scrutinise data over the next few days before announcing whether to go ahead with the full reopening on Monday.
Ministers are concerned that a two-week delay may need to be extended, increasing uncertainty for businesses.
They reportedly said a four-week delay would ensure more people in their 40s have received two vaccinations, with time factored in to allow immunity to take effect.
It is understood that the 30-person limit on wedding ceremonies will end on June 21, even if the easing of other restrictions is delayed.
There were a further 7,393 new Covid-19 cases on Thursday, with infections rising 63.2 per cent in the past seven days compared with the week before.
Danny Mortimer, deputy chief executive of the NHS Confederation, joined the calls for a delay to the end of restrictions.
"The government must now be ready to push back the June 21 deadline for easing restrictions further, to help abate rising infections, ease pressure on the NHS and keep the public safe."
But Health Secretary Matt Hancock refused to be drawn on whether restrictions would end, suggesting "the most important fact" was to analyse whether vaccines had broken the link between cases, deaths and serious illness.