People infected with the coronavirus variant found in the UK are up to 64% more likely to die than those with other strains

• A coronavirus variant first detected in the UK is deadlier than the original version of the virus.
• People infected with the strain, B.1.1.7, are 55% to 64% more likely to die from COVID-19.
• Existing vaccines seem to work against B.1.1.7, though other variants can evade vaccine-induced antibodies.

The data is in: People infected with the coronavirus variant first discovered in the UK have a higher risk of dying from COVID-19 than those who get other versions of the virus.

New research published Monday in the journal Nature found that among cases involving the variant, known as B.1.1.7, patients had a 55% higher chance of death within four weeks following their positive test.

The study authors examined roughly 2.2 million people who tested positive in England between September and mid-February, then compared the number of deaths among those with B.1.1.7 to those who were infected with other strains.

After controlling for variables including a patient's age, sex, ethnicity, and living arrangement, the researchers found that with the original virus, about six out of every 1,000 people in their 60s who test positive might be expected to die. But this number rises to about nine out of 1,000 with B.1.1.7.

"In spite of substantial advances in COVID-19 treatment, we have already seen more deaths in 2021 than we did over the first eight months of the pandemic in 2020. Our work helps to explain why," Nick Davies, the lead author of the study and an epidemiologist at the London School of Hygiene & Tropical Medicine, said in a press release.

In January and February, 42,000 people in England died of COVID-19.

Mounting evidence shows the B.1.1.7 variant is more deadly

B.1.1.7 was discovered outside London in September, but initial evidence suggested the strain wasn't more lethal. Then in January, UK Prime Minister Boris Johnson announced the variant was likely associated with higher mortality.

Research published last week in the journal BMJ confirmed that. It found B.1.1.7 to be deadlier than other strains - and even more deadly than the Nature study results suggest.

The BMJ researchers examined nearly 55,000 pairs of people in the UK. Within each pair, one person had tested positive for B.1.1.7 while the other had tested positive for a different coronavirus strain (including the variants from South Africa and Brazil). The members of each pair had similar ages, ethnicities, and geographic locations, and got their positive test results between October and February.

The study found the B.1.1.7 variant was 64% deadlier than the other strains within the four weeks following a positive test.

Johnson's January announcement was based on research collected by the UK's New and Emerging Respiratory Virus Threats Advisory Group, which found that on average, people infected with B.1.1.7 in the UK had a 30% higher mortality rate than those with the original virus.

A follow-up analysis from Public Health England analyzed data collected between late November and early January, and found that B.1.1.7 was 65% deadlier than other strains. Researchers from the University of Exeter, meanwhile, looked at samples collected between October and late January and found that people infected with the variant were almost twice as likely to die.

Higher mortality could be related to higher viral loads

The strain's increased lethality could be chalked up to the fact that people infected with B.1.1.7 have higher viral loads on average, meaning they produce more viral particles when they're infected. Higher viral loads, multiple studies show, are associated with a higher risk of death and more severe disease.

"That was the first thing that certainly came to my mind," William Schaffner, an infectious-disease expert at Vanderbilt University, previously told Insider. "It would make very good sense."

It's also possible that the strain's increased transmissibility simply gives the virus a better chance of infecting more people who are at higher risk of severe illness. A more transmissible strain means people are more likely to get infected if exposed; B.1.1.7 is between 50% and 70% more contagious than the original version of the virus.

This higher transmissibility could be due to several mutations in the genetic code for the virus' spike protein, which it uses to invade cells. These tweaks may make it easier for the B.1.1.7 variant to spread.

"It may simply be a matter of a more contagious virus getting to more vulnerable people who are older or have underlying health problems like diabetes or lung disease," Schaffner said.

Yet another possibility is that the variant's increased transmissibility indirectly contributed to a higher mortality rate due to the stress it put on the UK's healthcare system. The number of daily COVID-19 cases there skyrocketed in the four months following B.1.1.7's discovery, jumping from 3,899 new cases on September 20 to more than 68,000 cases on January 8.

The spike in cases strained UK hospitals and healthcare resources, which may have hurt patient outcomes.

"If your cases get out of control, your deaths will get out of control as your health system comes under pressure," Mike Ryan, executive director of the World Health Organization's health emergencies program, said in January.

Existing vaccines work against B.1.1.7

B.1.1.7 has been found in 94 countries, including the US.

But in recent studies, both Pfizer and Moderna found that their shots held up well against the variant. Other vaccines, including those from Johnsen & Johnsen and AstraZeneca, protect people from B.1.1.7, too.

But these shots seem less effective overall against the variant first discovered in South Africa, B.1.351, and the strain found in Brazil, named P.1.

That's likely because those two variants share a mutation that can prevent the antibodies generated in response to the original virus from recognizing them. This genetic tweak is mostly missing in B.1.1.7, though UK researchers did find 11 cases of B.1.1.7 with that mutation in a set of more than 200,000 samples.

Studies have not found either B.1.351 or P.1 to be more lethal than the original virus.