Coronavirus Variant Is Indeed More Transmissible, New Study Suggests

BY Mojgan December 26, 2020 Health ، Medical ، Science 1 views
A gazebo outside a bar in London on Dec. 15. The city and much of southeastern England has since returned to lockdown. Credit: Andrew Testa for The New York Times

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.”

Nicholas Davies, the lead author of the study, said that the model should also serve as a warning to other countries where the variant may have already spread.

“The preliminary findings are pretty convincing that more rapid vaccination is going to be a really important thing for any country that has to deal with this or similar variants,” Dr. Davies, an epidemiologist at the London School of Hygiene and Tropical Medicine, said in an interview.

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.”

A New Variant
A series of tiny mutations found in many British samples of the coronavirus may help the virus spread more easily. The coronavirus variant is known as B.1.1.7.
By Jonathan Corum | Source: Andrew Rambaut et al., Covid-19 Genomics Consortium U.K.

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.

Dr. Davies and his colleagues 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 in some regions of the U.K. because people in those places move around more and are 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 researchers concluded that the variant is able to spread to more people on average than other variants are. Dr. Davies cautioned that their estimate of 56 percent more contagious was still rough, because they are still gathering data about the variant’s most recent spread. “I think when we get more of that curve, we’ll be more certain,” he said.

Still, he said, even with the data he and his colleagues have so far, he felt confident that the new variant must be taken very seriously. “I do feel that with the totality of the evidence, it’s a strong case,” he said.

Dr. Davies and his colleagues 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.

Dr. Davies and his colleagues also took into account the protection that vaccines will provide. Vaccine experts are confident that coronavirus vaccines will be able to block the new variant, although that has to be confirmed by laboratory experiments that are now underway.

To look at the impact of the current rate of vaccinations, the researchers made a model in which 200,000 people were vaccinated each week. That pace was too slow to have much effect on the outbreak. “That kind of pace wouldn’t really be able to support much relaxation of any of the control measures,” Dr. Davies said.

But when they raised the vaccinations to 2 million a week, they saw a reduction in the peak burden on I.C.U.s. Whether the U.K. can ramp up vaccinations by a factor of 10 is unknown.

As of Tuesday, the variant had not been identified in the United States, according to the Centers for Disease Control and Prevention. “Given the small fraction of U.S. infections that have been sequenced, the variant could already be in the United States without having been detected,” they warned.

The United States is vaccinating its citizens more slowly than expected. That could potentially become a problem if the variant in the U.K. became widespread in the United States as well.

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

Dr. Davies cautioned that the model he and his colleagues analyzed 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.

They also did not take into account other tools for stopping the spread of the variant, such as an aggressive program to test people and isolate those who are infected. “That’s a limitation of the paper,” Dr. Davies said. The researchers are now starting to analyze new possibilities such as that one.

Still, Dr. Davies and his colleagues wrote in the conclusion to their study, “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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