LONDON — This is a puzzler. Coronavirus cases are plummeting in Britain. They were supposed to soar. Scientists aren’t sure why they haven’t.

The daily number of new infections recorded in the country fell for seven days in a row before a slight uptick Wednesday, when the country reported 27,734 cases. That’s still almost half of where the caseload was a week ago.

The trajectory of the virus in Britain is something the world is watching closely and anxiously, as a test of how the delta variant behaves in a society with relatively high vaccination rates. And now people are asking if this could be the first real-world evidence that the pandemic in Britain is sputtering out — after three national lockdowns and almost 130,000 deaths.

Public health experts, alongside the government, predicted that cases would be rising in Britain at this point, perhaps even exponentially.

The highly contagious delta variant of the virus, first detected in India, accounts for almost all new cases here. On July 17, the number of new day cases reached 54,674, the highest since January.

Two days later, dubbed “Freedom Day” by the press, Prime Minister Boris Johnson’s government ended almost all government mandates in England for mask-wearing and social distancing. Pubs are serving pints at the rail and night clubs have reopened with maskless youths packed on the dance floors. Viral defense is now a “personal choice.”


And so some of the best infectious-disease modelers on the planet warned that 100,000 new cases a day this summer could be expected.

But the trend since then has been on a sharp decline.

Scientists have theories. Maybe it’s the sunshine? There was a weeklong heat wave.

Schools have closed for the summer break, so children are not spreading the virus as much.

Test-and-trace might be working. Last week, almost 620,000 people were pinged by a National Health Service app in England and Wales telling them to quarantine after exposure to the virus.

It is also possible that people have stopped getting tested — because if they test positive, even if they are fully vaccinated, they are asked to quarantine for 10 days, even if they are about to travel abroad for their holidays.


Or maybe Britain has reached an immunity threshold. More than 70 percent of adults here are fully vaccinated, and 88 percent have had a first dose — one of the best vaccine uptakes in the world. Among those who remain unvaccinated, many have had COVID or asymptomatic infection.

Britain could be approaching “population immunity, with people immune either from vaccinations or natural infection,” said Paul Hunter, a professor in medicine at the University of East Anglia.

He noted that the reverb from Freedom Day wouldn’t be instantaneous. Any bump in cases would start to show up later this week or early next, as symptoms can appear up to two weeks after exposure. But he predicted, overall, “we won’t see the huge surges that we’ve seen in the past.”

Martin McKee, professor of European public health at the London School of Hygiene and Tropical Medicine, said he doubted that Britain was reaching population or herd immunity, in part because that wouldn’t explain regional differences. “I don’t have a simple answer, none of us do,” he said.

Johnson is not celebrating. Not yet.

Speaking to reporters on a rainy Tuesday from under an unusually smallish umbrella, the prime minister said that, yes, he has noticed the “better figures.”

But he added: “It is very, very important that we don’t allow ourselves to run away with premature conclusions about this.”


“People have got to remain very cautious, and that remains the approach of the government,” he said.

Hospitalizations and deaths are still rising, though at a far slower rate than during previous waves. More than 6,000 COVID patients are in hospitals in Britain, the highest figure since March. On Wednesday, Britain reported 91 new deaths.

But the people so want the pandemic to end. The Daily Mail’s front page Wednesday declared: “COVID is all over bar the shouting.”

On Wednesday, the government announced that fully vaccinated visitors from the United States and Europe could travel to England starting Aug. 2 without quarantining. The reverse is not true, however. Even as England is reopening, the United States has kept restrictions for travelers from Britain and the E.U. in place.

Stephen Griffin, an associate professor at the University of Leeds, said the reduction of cases was “very, very strange.”

He cautioned that further data needs to be analyzed but suggested that it could be a result of a raft of behavioral factors, ranging from the warm weather to people following quarantine guidance to people avoiding tests if they want to go on vacation. Another factor is the end of the Euro 2020 soccer tournament, which drove thousands into pubs and onto the streets.


“All of these things compounded together may genuinely reflect a reduced number of tested positive cases,” he said. “Whether that actually reflects infection or not, we don’t know.”

Neil Ferguson, an epidemiologist at Imperial College London whose models have shaped government policy in Britain and the United States, said it now appears possible that the pandemic could be in the rearview mirror.

He added his own notes of caution, too. He told the BBC on Tuesday that the effects of lifting restrictions on Freedom Day earlier this month have yet to be seen.

Ferguson also said there could be a spike in cases if the weather turns bad or when schools return in September.

“We’re not completely out of the woods,” he said. “But the equation has fundamentally changed. The effect of vaccines has been huge in reducing the risk of hospitalizations and death. And I’m positive that by late September or October … we will be looking back at most of the pandemic.”

Ferguson added: “We will have COVID with us. We will still have people dying from COVID. But we’ll have put the bulk of the pandemic behind us.”