COVID-19: Is the B.1.1.7 variant more lethal?

• A new variant of SARS-CoV-2, which is the virus that causes COVID-19, was first detected in the United Kingdom in September 2020.
• The variant, called B.1.1.7, is known to spread more easily than older variants of the virus.
• A new study adds to evidence that B.1.1.7 is also more deadly than previous variants.
• Compared with older variants, the new variant caused around 64% more deaths in pairs of individuals matched for factors such as age, gender, and ethnicity.

In early September 2020, scientists detected a new variant of SARS-CoV-2 in the south-east of England that is more transmissible than older variants.

By the end of 2020, the new variant — called B.1.1.7 — had spread across the United Kingdom and accounted for three-quarters of all infections.

To date, the new variant has spread to at least 94 countries worldwide, including the United States, where there have been more than 3,000 confirmed cases.

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A previous study, reported by Medical News Today, found that B.1.1.7 is associated with a 35% higher mortality rate among those who test positive for SARS-CoV-2 in the community.

However, research at the University of Bristol and the University of Exeter in the U.K. now suggests that the increased mortality risk may be as much as 64%.

The scientists compared the mortality rates for 54,906 matched pairs of participants who tested positive for older variants of the virus or B.1.1.7 in community testing.

To account for other factors that could affect mortality risk from COVID-19, the scientists matched each pair of participants for the following:

• age
• sex
• ethnicity
• deprivation level
• location
• date of positive test

All the participants tested positive between October 1, 2020, and January 29, 2021, and the researchers followed them until February 12, 2021.

According to their analysis, patients with a B.1.1.7 infection were between 32–104% more likely to die from the infection within 28 days of a positive test.

The most likely increase in mortality risk with the new variant is close to the middle of this range, at around 64%, say the researchers.

This equates to an increase in the number of deaths from 2.5 to 4.1 per 1,000 people who test positive for SARS-CoV-2 in the community.

The study appears in the BMJ.

Substantial challenge

“This increased lethality, in addition to the increased transmissibility, means that this version of the virus presents a substantial challenge to healthcare systems and policymakers,” said Dr. Simon Clarke, Associate Professor in Cellular Microbiology at the University of Reading in the U.K., who was not involved in the research.

“It also makes it even more important people get vaccinated when called,” he told the Science Media Centre in London.

The authors of the new study were able to deduce which patients acquired a B.1.1.7 infection thanks to a glitch in the polymerase chain reaction (PCR) test for the virus.

The test works by amplifying the sequences of three of the virus’s genes, but the new variant has a mutation in one of these — a gene that codes for its spike proteins.

The mutation prevents the amplification of this gene in B.1.1.7, so the test detects only two out of the three genes. This allows researchers to estimate how many people of those tested have contracted the new variant.

“It was fortunate the mutation happened in a part of the genome covered by routine testing,” says one of the authors, Ellen Brooks-Pollock, Ph.D., senior lecturer in veterinary public health at the University of Bristol.

“Future mutations could arise and spread unchecked,” she adds.

The researchers hope their study will inform government and health officials’ response to this variant and others that are likely to emerge.

Senior author Leon Danon, Ph.D., associate professor in infectious disease epidemiology and data analytics at the University of Bristol, warns:

“SARS-CoV-2 appears able to mutate quickly, and there is a real concern that other variants will arise with resistance to rapidly rolled out vaccines. Monitoring for new variants as they arise, measuring their characteristics, and acting appropriately needs to be a key part of the public health response in the future.”

Potential biases

The authors note that by using matched pairs of patients, they could control for several potential biases in their estimate of increased mortality with B.1.1.7.

In particular, they matched each pair according to where they lived and the date of their positive test result.

This helped account for possible variations in hospital care, which came under increasing pressure as a second wave of infections began in the U.K. in autumn 2020.

However, Dr. Julian Tang, consultant virologist at the University of Leicester in the U.K., told the Science Media Centre that he remained unconvinced by the results.

He pointed out that the researchers did not match participants for pre-existing conditions — known as “comorbidities” — that predispose [people] to more severe COVID-19, including diabetes and hypertension.

“Clinical teams know that the coldest winter temperatures occurring in January or February can exacerbate all the comorbidities that predispose to more severe outcomes of COVID-19,” he said.

He suggested that further analysis of COVID-19 outcomes during warmer months would be needed to account for the differential effects of the weather on people with these comorbidities.

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