British hospitals were flooded with COVID-19 patients.Credit: Kirsty Wigglesworth / AFP via Getty
The news is worrying, but complicated. Scientists released the data behind a British government warning last week that the rapidly spreading SARS-CoV-2 variant B.1.1.7 increases the risk of death from COVID-19 compared to previous variants. But some scientists warn that the latest study – like the government’s warning – is preliminary and does not yet indicate whether the variant is more deadly or is just spreading faster and reaching more vulnerable people.
The latest findings are worrying, but to draw conclusions “more work needs to be done,” says Muge Cevik, a public health researcher at the University of St Andrews, who lives in Edinburgh, UK.
Last week, British Prime Minister Boris Johnson said that preliminary data from several research groups suggested that B.1.1.7, which was first identified in the UK, was spreading faster than previous variants and it was also associated with an increased risk of death. On February 3, researchers at the London School of Hygiene & Tropical Medicine (LSHTM) released an analysis1 of some of these data, which suggests that the risk of dying is about 35% higher for people confirmed as infected with the new variant.
In real terms, this means that for men aged 70-84, the number of people likely to die from COVID-19 increases from about 5% for those who test positive for the older variant, to more than 6% for those confirmed infected with B.1.1.7, according to the analysis. For men aged 85 and over, the risk of dying increases from about 17% to almost 22% for those with confirmed infection with the new variant. The analysis was not peer-reviewed.
Other groups are also studying whether B.1.1.7 and other new variants of SARS-CoV-2 are more lethal than previous versions of the virus.
Dominant variant
Since B.1.1.7 was first identified in September in southern England, it has become the dominant variant in the United Kingdom and has spread to more than 30 countries. To investigate whether the strain causes an increased risk of death, Nicholas Davies, an epidemiologist at LSHTM, and colleagues analyzed data from more than 850,000 people who were tested for SARS-CoV-2 between November 1 and January 11, but who were not at the hospital .
Despite the fact that variant B.1.1.7 was new, the researchers were able to identify infected people because of a flaw in a standard diagnostic kit used in the UK. The test normally looks for three SARS-CoV-2 genes to confirm the presence of the virus. But in the case of B.1.1.7, changes in the spike protein mean that people who are infected still test positive, but for only two of those genes.
The team found that B.1.1.7 is more deadly than previous variants for all age groups, genders and ethnicities. “This provides strong evidence that there is indeed an increase in mortality with the new strain,” said Henrik Salje, an infectious disease epidemiologist at the University of Cambridge in the United Kingdom.
Although Cevik says that the small number of deaths among young people included in the analysis is not enough to conclude that the new variant affects all ages equally. “It really seems to be affecting older age groups,” she says.
This is expected, as the chances of dying from COVID-19 increase significantly with age, says Tony Blakely, an epidemiologist at the University of Melbourne in Australia.
The findings are also consistent with other preliminary work summarized in a document published on January 22 by the New and Emerging Respiratory Virus Threat Advisory Group (known as NERVTAG), a government advisory group. A research team at Imperial College London found that the average fatality rate – the proportion of people with COVID-19 confirmed to die as a result – was about 36% higher for people infected with B.1.1.7.
Other explanations
Cevik says more data and analysis are needed to conclude whether the variant is more deadly than other strains. For example, the latest study does not consider whether people infected with the variant have underlying comorbidities, such as diabetes and obesity, and are therefore more vulnerable and at greater risk of dying, she says.
The study also covers only a small fraction of deaths from COVID-19 in the UK – about 7% – and the effect may disappear if deaths in people tested in hospitals are included, says Cevik. Preliminary work by other groups has not found an increased risk of death in people admitted to hospitals with the new variant, and this complicates the most recent results.
Davies says it is possible that the new variant may be causing more serious illness, resulting in more people ending up in the hospital, but that, once there, the risk of dying may be the same as before. But he agrees that more data is needed before researchers can understand what is going on.
Some researchers also suggested that B.1.1.7 could contribute to an increase in deaths due to its rapid spread, which would overburden hospitals and affect the quality of care. But Davies says he and his team dismissed this because they compared the risks of death associated with the newer and older variants for people who were tested at the same time and place and would therefore be subject to the same conditions in hospitals.