The government lowered the quarantine requirement in England—the U.K.’s other devolved administrations make their own health policy—to seven days from 10 last week, but is facing calls to go further after the U.S. Centers for Disease Control and Prevention shortened its recommendation to five days.

The government wants to ensure the recent change “is working as we believe it ought to,” U.K. minister Chloe Smith told the BBC on Wednesday. There are no current plans to amend it, she said.

It’s the latest example of the balancing act facing Johnson over COVID-19. Under intense pressure from members of his ruling Conservative Party, his government announced there would be no new curbs before the New Year to tackle the new Omicron variant even as cases break records almost daily.

Johnson was asked Wednesday why he has refrained from new restrictions even as Wales, Scotland and Northern Ireland get tougher. He said the government “looked at the balance of risks,” and he cited the impact of booster shots in preventing serious illness from Omicron.

But he also urged people to get tested, even amid reports of shortages of the rapid lateral flow tests the government wants people to use. Leyla Hannbeck, chief executive of the Association of Independent Multiple Pharmacies, told the BBC that supplies of COVID-19 tests in pharmacies are low and “inconsistent.”

That has implications for the debate on isolation periods, because under the current rules people are able to end quarantine if they show negative tests on days 6 and 7 after testing positive.

Meanwhile, evidence that the Omicron variant causes milder disease is fueling demands for remaining restrictions and rules to be eased, and some Tory-leaning newspapers have highlighted the impact of quarantining staff on the economy. Some business lobbies are also backing a reduction in quarantine times.

A total of 9,546 people were in the hospital in England with COVID-19 as of Dec. 28, according to the latest official figures, the highest since March but far lower than the winter peak of 34,336 in January.

“We have got to go for as low an isolation period as is safe to do, because the disruption that is being caused at the moment is huge,” Confederation of British Industry President Karan Bilimoria told Sky News on Wednesday.

But while staff absence is also a “huge issue” for the health service, Matthew Taylor, chief executive of the NHS Confederation, said any move to cut isolation times would need “clear evidence” that it wouldn’t trigger a rise in infections.

“The hospitals are full of people who are very vulnerable and, for those people, even a relatively mild form of the virus can have serious consequences,” he told BBC radio on Wednesday. “So whilst anyone in the NHS would be delighted if people were able to come back to work earlier—if they are safe—we need to be absolutely sure that that is the case.”