Public health experts in the United Kingdom are calling on the government to reintroduce some coronavirus restrictions as cases climb — far outstripping those of its Western European neighbors — despite the country’s high vaccination coverage.

The U.K.’s coronavirus case count could rise to as high as 100,000 a day, Health Secretary Sajid Javid said at a news conference Wednesday. But that was not grounds for the government to abandon its “Plan A,” he said, and impose more restrictions — at least not yet.

“We think it is the right decision to learn to live with this virus,” such as “asking people to take more responsibility” for measures such as masks and vaccinations, Javid said.

Other public health experts warn that Britain is, once more, facing a critical juncture: impose restrictions now before this wave becomes too big to contain.

“We are right on the edge — and it is the middle of October,” Matthew Taylor, chief executive of the National Health Service Confederation, a group representing the health-care systems in England, Wales and Northern Ireland, told the Guardian newspaper Tuesday. “It would require an incredible amount of luck for us not to find ourselves in the midst of a profound crisis over the next three months.”

Prime Minister Boris Johnson ended the lockdown in England on July 19, declaring it “Freedom Day.” Since then, the country has lifted most restrictions, with no legal mask requirement in most settings, including schools, and nothing approaching a universal vaccine mandate, in sharp contrast with some other European countries.

In a speech in September laying out his government’s plan for autumn and winter, Johnson said he would like things to continue that way, with an emphasis on promoting vaccinations, booster doses and frequent testing, rather than reintroducing restrictions. However, he outlined a pandemic “Plan B” that he said could be necessary if the publicly funded NHS became overwhelmed. Some restrictions could then be introduced, including advising people to work from home, legally mandating face coverings in certain settings again, and bringing about mandatory covid passports.

Now, as the United Kingdom this week recorded its highest number of deaths from the coronavirus since March, health experts are warning of a “winter crisis” and have begun urging the government to not just implement “Plan B” — but to go further with “Plan B Plus.”

The government should ensure “clear communications to the public that the level of risk has increased,” Taylor’s organization said in a news release, and call on the public to “mobilise around the NHS and do whatever they can to support frontline services this winter,” including by getting booster shots and volunteering.

“Many of these measures, particularly around mask-wearing and covid-19 certification, are already common in parts of Europe where the prevalence of the disease is lower,” the group added.

However, the government, which has been keen to reopen the economy, has insisted that its approach is working. Business Secretary Kwasi Kwarteng said Wednesday that it was not the time for Plan B, adding: “What we want to do is manage the situation as it is — we don’t want to go back into lockdown and further restrictions. I would rule that out.”

The Cabinet Office said in an emailed statement: “The vaccination programme has significantly weakened the link between cases, hospitalisations and deaths and will continue to be our first line of defence against COVID-19.”

“We always knew the coming months would be challenging, which is why we set out our plan for Autumn and Winter last month.”

Daily case numbers are the highest they have been since July — 49,156 people were reported to have tested positive for the coronavirus in Britain on Monday. And “the problem is a lot worse than the daily figures suggest,” said Robert West, a professor of health psychology at University College London who is part of the government’s Scientific Pandemic Insights Group on Behaviors.

This is because not everyone who has contracted the virus is aware of it, particularly if they do not have symptoms, and some people may test positive but not report their result to public health bodies. The Office for National Statistics estimates that the true number of infections in England, in the week ending on Oct. 9, was closer to 1 in 60 people in the country.

And while hospitalizations and deaths remain low, they are climbing. According to the government, in the United Kingdom as a whole, 954 people were recorded to have died of covid-19 in the past seven days, a 21 percent week-on-week increase, while 6,074 people were reported to have been admitted to a hospital because of covid-19 in the seven days leading up to Saturday, an 11 percent week-on-week increase.

Experts say three major trends may have led Britain to this point: loosened public health restrictions, the relative success of vaccination campaigns and the natural evolution of the virus.

The government went into “an explicitly post-pandemic mode” and did not do enough to mitigate risks after Johnson ended lockdown, said Danny Altmann, professor of immunology at Imperial College London. This created a “perfect storm” once the more contagious delta variant began to spread, while schools reopened, immunity from the coronavirus vaccines began to diminish and the weather got cooler.

The success of the country’s vaccination program may also be a factor in the rising number of cases right now. While much is still unknown about how coronavirus vaccines work, studies suggest their efficacy could be reduced over time. Because many people were vaccinated early, immunity to infections could be going down around now, said West, of University College London, just as people begin to spend more time indoors, potentially increasing transmission.

The virus mutates naturally over time, so some of the rising cases could also be explained by “basic biology and timeline,” Altmann said. “Not only were we early, we were also at the front of the queue for importation of delta variant, so we’ve had much longer for it to percolate,” he said, adding that the same is true for AY4.2, a new variant sometimes known as “delta plus” that is “expanding” in England, according to the latest official analysis.

And while nearly 79 percent of those older than 12 have been fully vaccinated, efforts to vaccinate school-age children have progressed more slowly — even though infections are rising in that age group. The latest official data shows an estimated 8.9 percent of children in England in what roughly translates to sixth to 10th grade were infected.

While the government has remained reluctant to reintroduce covid restrictions, it has said it will keep “a very close eye” on case numbers.

It has delayed implementing covid measures in the past, partly out of concern that the public would not comply, according to a recent scathing review of the British response to the pandemic. In that review, lawmakers concluded that the government underestimated people’s willingness to comply with restrictions and erred in delaying a lockdown as a result.

Now, some health experts say the public would be willing to accept more restrictions again if they are sold as common-sense measures.

Research shows most people would be willing to start wearing masks again “if you make it very clear in your communications why and when to do it,” West said.

Altmann had a more blunt assessment: “I don’t understand how people can get bored of avoiding death.”

Read more: