Coronavirus subvariant JN.1 growing fast, already dominant in parts of the US

By Brenda Goodman | CNN

The US Centers for Disease Control and Prevention estimates that the coronavirus subvariant JN.1 is now causing about 20% of new Covid-19 infections in this country, and it’s the fastest-growing strain of the virus. It’s already dominant in the Northeast, where it is estimated to cause about a third of new infections.

JN.1 is descended from BA.2.86, or Pirola, a subvariant that came to the world’s attention over the summer because of the large number of changes to its spike proteins: more than 30. Scientists feared that it was so mutated that it would completely escape the protection of vaccines and antibodies against Covid-19, perhaps sparking another tidal wave of illness the way the original Omicron variant did in 2021.

That never happened, but BA.2.86 hung around, growing very slowly in some countries, including the US. Some studies suggested that it never really took off because it may have lost some of its ability to infect our cells.

Enter JN.1, which is two generations removed – a granddaughter, so to speak – of BA.2.86. JN.1 has only one change to its spike protein compared with its ancestor, but that seems to have been enough to make it a fitter and faster virus.

The CDC estimates that prevalence of JN.1 more than doubled in the US between late November and mid-December. It seems to be getting an assist from holiday travel and waning immunity.

“When I just look at the growth curve, it is rising quite sharply, and it seems to coincide with the Thanksgiving break in terms of timing,” said Dr. Shishi Luo, who heads infectious diseases for the genomic sequencing company Helix.

Variant trackers say they expect it to become the leading coronavirus variant around the world in a matter of weeks.

“It’s already pretty clear that it is highly competitive with existing XBB variants and looks like it’s on track to become the next sort of globally dominant group of variants,” said Dr. T. Ryan Gregory, an evolutionary biologist at the University of Guelph in Ontario, who has been tracking the evolution of the virus that causes Covid-19.

The mutation in JN.1’s spike is at a position that Gregory said seems to help the virus escape our immunity.

Studies by researchers at Columbia University and in China suggest that there’s about a twofold decrease in the ability of our antibodies to neutralize this subvariant. Although that’s not a huge drop, it could portend another wave of infections on the horizon.

Several countries in Europe – including Denmark, Spain, Belgium, France and the Netherlands – have seen exponential growth of JN.1 and, with it, rising hospitalizations. It’s also growing quickly in Australia, Asia and Canada.

That’s happening in the United States too, thanks to waning immunity. Too many Americans have chosen to forego the latest round of vaccination for Covid-19, and they may also have passed it up last year. As a result, their immunity hasn’t had the important upgrades that help the body fend off the worst consequences of Covid-19 infections.

As of December 9, only about 18% of adults had received the latest Covid-19 vaccine, about the same low proportion of the population that got them last year, according to the CDC.

The CDC has called on doctors to work harder to get their patients vaccinated, emphasizing that it’s not too late in the season to benefit from the shots.