Delta variant can be held in check

The latest surge of Covid-19 cases in the U.K. is giving rise to growing optimism among doctors and scientists that the highly transmissible Delta variant of the coronavirus can be held at bay with high levels of vaccination and public caution.

Although caseloads are now ticking higher after Prime Minister Boris Johnsondropped almost all public-health restrictions in mid July, hospital admissions have been falling and deaths are a fraction of the level seen in earlier phases of the pandemic, according to the latest official data through early August.

The U.K. experienced a wave of Delta-driven infections earlier than other Western nations and has achieved broader vaccine coverage than many of its peers, including the U.S., making it a test case for how well the shots can push Covid-19 into the background alongside other common respiratory ailments. The government also publishes significant amounts of data that allow the course of the pandemic to be closely tracked.

Between 90% and 94% of British adults have some degree of immunity to coronavirus from full or partial vaccination, or prior infection, the U.K. statistics office estimates, based on statistical analysis of blood samples. That is almost certainly playing a big role in keeping a lid on cases and ensuring subdued hospital admissions and deaths, say scientists, though school holidays, warm weather and other factors are also pushing against transmission.

A key test will come in the fall, doctors and scientists say, when schools return and colder temperatures drive people indoors, where the virus can spread more easily. How severe any winter resurgence will be is unclear.

“There will inevitably be an increase in cases, that’s a given,” said Tom Wingfield, an infectious-disease physician in Liverpool, England. “It’s just a case of how much it rises and what that means for hospitalization rates.”

The seven-day average of new Covid-19 cases in the U.K. stood at 28,007 Tuesday, down 41% from a peak of almost 48,000 nearly three weeks ago. For five days straight, the seven-day average has been increasing and is now above the 14-day average of new daily cases, signs that caseloads are growing again after a long stretch of decline.

For now, the pickup is modest, with cases up around 7% since the trend reversed course. Epidemiologists say such reversals and fluctuations in daily case counts are to be expected at this stage of the pandemic, as vaccines push transmission down and increasing social interactions push it up.

The U.K. data underscore the effectiveness of vaccines at limiting severe illness and death. Fifty-nine percent of the whole population, and three-quarters of adults, are fully vaccinated, compared with half and 61% in the U.S., respectively.

Hospital admissions in the U.K. in January peaked at more than 4,200 a day. In July, admissions hit a high of around 900 a day and on the latest data are averaging 760 and falling. Deaths in January reached 1,200 daily and are currently averaging around 90 a day.

Data compiled by Google, a unit of Alphabet Inc., suggests many people are following Mr. Johnson’s advice to be cautious once restrictions eased. In early August, visits to restaurants, shopping malls and recreational settings such as cinemas were around 7% below pre-pandemic levels. Public-transport use is a third lower. Visits to workplaces are 40% lower.

Around 70% of Britons still wear a mask in public places, according to polling by YouGov PLC, a proportion that hasn’t changed much since spring 2020. In the U.S., less than half of those polled by YouGov say they wear a mask, down from more than 80% in late last year.

Paul Hunter, an epidemiologist and professor of medicine at the University of East Anglia, said he thinks the U.K. is closing in on a state of endemic equilibrium, where vaccines mean the virus isn’t likely to fuel significant new waves of sickness as in the past but it can still cause sporadic outbreaks, especially in less-protected areas of the country. Case rates are already uneven, he said, with flatlining or falling infections in previously hard-hit areas or those with high vaccine uptake, and increasing caseloads in more-exposed regions.

Scientists at the Medical Research Council Biostatistics Unit at the University of Cambridge estimate the infection fatality rate for Covid-19—the proportion of those infected who die—has fallen to 0.14% in the U.K., from a peak of 1.86% in January, when the pandemic was at its fiercest. For the over 75s, who are more at risk of developing severe illness than younger age groups, the estimated infection fatality rate has declined to 2.3% from close to 20%.

Data shows this wave of Covid-19 has resulted in a greater proportion of younger people being admitted to hospitals. Figures from the state-run National Health Service show 21% of admissions in the week through Aug. 1 were those age 18 to 34, compared with around 5% in January.

Though studies have shown Delta is more transmissible than earlier variants of the virus and puts people at a higher risk of hospitalization, scientists say there is no evidence the variant is more dangerous for young people than it is for older people. The higher proportion of younger people in hospital admissions in Britain reflects patterns of vaccination, as older age groups were prioritized for the shots, which are highly effective at preventing severe illness and death. Younger people also tend to socialize more and are at greater risk of infection.

“I don’t think the virus has any predilection for young people,” said Aziz Sheikh, director of the Usher Institute, the medical school at the University of Edinburgh.

Kamlesh Khunti, a physician and professor of primary-care diabetes and vascular medicine at the University of Leicester, said Covid-19 patients in his district this time around have been younger and recovered quickly. Some were admitted for another reason and were diagnosed with Covid-19 once in hospital, he said.

“Recovery rates are better,” he said. Sicker patients have tended to be those with some underlying health condition that worsens symptoms, Prof. Khunti said.

Some doctors say they have bigger problems than Covid-19 this summer, such as a backlog of patients and staff absences due to ill health and isolation from coming into contact with someone infected with the virus. Nathan Spence, a doctor working in an acute admissions unit in a hospital in Oxford, England, said he is currently treating around 30 Covid-19 patients, compared with 250 to 300 in January. “The biggest barrier to us working at the minute is staff being off work,” he said. Live Mint