Coronavirus Variant Is Indeed More Transmissible, New Study Suggests

A team of British scientists released a worrying study on Wednesday of the new coronavirus variant sweeping the United Kingdom. They warned that the variant is so contagious that new control measures, including closing down schools and universities, might be necessary. Even that may not be enough, they noted, saying, “It may be necessary to greatly accelerate vaccine rollout.”

The study, released by the Center for Mathematical Modeling of Infectious Diseases at the London School of Hygiene and Tropical Medicine, has not yet undergone review by a scientific journal. The study compares a series of models as predictors of data on infections, hospitalizations and other variables; other researchers are studying the variant in laboratory experiments to determine if it is biologically distinct.

The study found no evidence that the variant was more deadly than others. But the researchers estimated that it was 56 percent more contagious. On Monday, the British government released an initial estimate of 70 percent.

Bill Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health who was not involved in the study, said that it presented a compelling explanation of the past and potential future of the variant.

“The overall message of it is solid and consistent with what we’ve been seeing from other sources of information,” he said in an interview. “Does this matter? Yes. Is there evidence for increased transmission? Yes. Is that going to impact the next few months? Yes. Those are all, I think, pretty solid.”

The variant, which came to the attention of British researchers earlier this month, has been rapidly spreading in London and eastern England. It carries a set of 23 mutations, some of which may make it more contagious.

The authors of the study found more evidence that the variant does indeed spread more rapidly than others. For example, they ruled out the possibility that it was becoming more common because outbreaks had started in places where people were more likely to come into contact with each other. Data recorded by Google, indicating the movements of individual cellphone users over time, showed no such difference.

The researchers built different mathematical models and tested each one as an explanation for the variant’s spread. They analyzed which model of the spread best predicted the number of new cases that actually were confirmed, as well as hospitalization and deaths.

The team then projected what the new variant would do over the next six months and built models that factored in different levels of restrictions. Without a more substantial vaccine rollout, they warned, “cases, hospitalizations, I.C.U. admissions and deaths in 2021 may exceed those in 2020.”

Closing schools until February could buy Britain some time, the researchers found, but lifting those extra restrictions would then cause a major rebound of cases.

Because of the higher transmission rate, the country will need a much higher percentage of the population to get vaccinated to reach herd immunity. To reduce the peak burden on I.C.U.s, the researchers found, vaccination would need to jump to two million people per week from the current pace of 200,000.

“You need to be able to get whatever barriers to transmission you can out there as soon as possible,” Dr. Hanage said.

The researchers warned that their model was based, like any model, on a set of assumptions, some of which may turn out to be wrong. For instance, the rate at which infected people die from Covid-19 may continue to drop as doctors improve at caring for hospitalized patients. Uncertainties remain as to whether the new variant is more contagious in children, and if so, by how much.

Still, they wrote, “there is an urgent need to consider what new approaches may be required to sufficiently reduce the ongoing transmission of SARS-CoV-2.”

Alessandro Vespignani, director of the Network Science Institute at Northeastern University in Boston, who was not involved in the study, said of the new estimates, “Unfortunately, this is another twist in the plot.”

“While we were all rejoicing for the vaccine,” he added, “here is the possibility of a change of epidemiological context that makes our next few months much more complex and more perilous to navigate. Evidence is accumulating that the variant is more transmissible, and this implies that it will likely require an even greater effort to keep spreading under control.”

Dr. Hanage cautioned that the model had some shortcomings. The researchers assumed that all people younger than 20 had a 50 percent chance of spreading the disease. Although that might be true for younger children, Dr. Hanage said, it is not for teenagers. “That’s the weakest part of their model,” he said.

Nonetheless, he said, the study provided an important glimpse into the country’s possible futures. “It’s not a forecast, it’s not a prediction, it’s not saying this will happen,” he said. “It is saying that if you don’t take it seriously, this is the kind of thing that could very easily happen.”

Benjamin Mueller contributed reporting.

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