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Update (March 10): One of the studies included in the NERVTAG report has been published in The BMJ today with expanded data. The researchers compared more than 100,000 people who tested positive for either B.1.1.7 or other SARS-CoV-2 variants, and found that B.1.1.7 was associated with a 32–104 percent increased risk of death within 28 days.

The B.1.1.7 variant of SARS-CoV-2, which was first found in September and is now dominant in the UK and present in many other countries, is thought to be more easily transmitted than other variants are. It might also be more deadly. UK Prime Minister Boris Johnson announced at a news conference on Friday (January 22) that new data indicate B.1.1.7 may be 30 percent more fatal.

The evidence comes from two analyses reviewed by a government committee called the New and Emerging Respiratory Virus Threats, or NERVTAG. Patrick Vallance, Johnson’s chief scientific adviser, said at the news conference that the 30 percent would mean that, for example, where before about 10 of every 1,000 60-year-olds who contracted COVID-19 would die, the rate for those with a B.1.1.7 infection would go up to 13 or 14 deaths per 1,000 cases. He urged caution in interpreting the numbers, saying in remarks quoted by USA Today, “I want to stress there’s a lot of uncertainty around these numbers and we need more work to get a precise handle on it, but it obviously is a concern that this (variant) has an increase in mortality as well as an increase in transmissibility.”

The US Centers for Disease Control and Prevention forecast earlier this month that B.1.1.7 will become the dominant strain of SARS-CoV-2 circulating in the country in March. “Increased SARS-CoV-2 transmission might threaten strained health care resources, require extended and more rigorous implementation of public health strategies, and increase the percentage of population immunity required for pandemic control,” the agency warned.

Maria Van Kerkhove, the World Health Organization’s technical lead on COVID-19, tells the Associated Press that the contagiousness and deadliness of new variants are being studied, and that so far her team hasn’t observed that they are more likely to cause severe disease, but that more-transmissible variants could lead to overwhelmed healthcare systems and thus, indirectly, to more deaths.

Luciana Borio, a COVID-19 advisor to President Joe Biden’s administration, makes a similar suggestion in comments to USA Today. “At minimum, I’d like to see data that this virus is causing some higher viral loads or some kind of mechanism that could explain the direct impact,” she says. “We don’t have any evidence that it’s a biological phenomenon.”

Yale University immunologist Akiko Iwasaki tells the newspaper that the news makes measures such as wearing a mask, avoiding crowds indoors, and getting vaccinated even more important.

“Honestly, the more you can avoid interaction altogether, the better,” she says. “Obviously some people don't have that luxury.”