New Covid variants fuel fears of summer surge in cases

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New variants of Covid-19 are spreading around the world and stoking fears of a summer surge in cases in the United States, the latest sign of the infectious disease’s capacity to mutate and potentially threaten herd immunity.

K.P. 2, one of several so-called FLiRT variants — the word derives from the names of mutations in the variants’ genetic code — has become the dominant strain of coronavirus in the United States since its emergence in March.

In the two weeks leading up to May 11, KP. 2 accounted for 28.2 percent of cases, compared to just 3.8 percent in the two weeks leading up to the end of March, according to the latest data from the U.S. Centers for Disease Control and Prevention. The KP1.1 variant has also grown rapidly to account for 7.6 percent of infections.

The agency is closely monitoring FLiRT variants – including the KP strains and the previously dominant JN.1 strain which are all offshoots of the dominant Omicron Covid strain – but does not believe there is evidence that this will lead to an increase cases of serious illness.

Four and a half years into the pandemic, the number of cases in the United States has fallen near its lowest level in recent months. But even though many infectious disease experts don’t expect an increase in hospitalizations, they warn that this new group of variants could cause a summer wave of infections.

A key question is how effective current vaccines will be against the new strains. Lawrence Young, a virologist at the University of Warwick, said booster shots would continue to offer useful protection, at least against severe disease.

However, William Schaffner, an infectious disease specialist at Vanderbilt University in Nashville, Tennessee, argued that protection “is not as guaranteed against these subvariants because the mutations are a little further away from the type of protection by antibodies that we obtained during a previous infection and vaccination. “.

“But this evidence comes from laboratory studies, we need to see what happens on the ground,” Schaffner added.

The U.S. Food and Drug Administration’s vaccine advisory committee will meet at the end of the month to discuss recommendations for mixing variants of next winter’s Covid vaccines. He postponed the meeting from early May so he could compile more data on the latest strains.

In Europe, the World Health Organization said FLiRT variants had been detected in 14 countries in Europe as well as Israel.

However, the European Center for Disease Prevention and Control said Covid activity “remained low” across the continent “although a small number of individual countries are showing slight increases in detections from very low levels “.

She had also observed “a limited number of detections” for JN. 1.7 and KP. 2, the two variants that had increased proportionally in the United States.

Officials from the UK Health Security Agency said on Friday that several FLiRT strains were circulating in the UK at low levels, although some appeared to be increasing in proportion to cases sequenced.

Young said the latest data indicated that infections in the UK with the FLiRT variants, which had “outpaced some of the other variants”, were likely similar to levels seen in the US. These strains are also increasingly prevalent in other countries, including Canada, Australia, Thailand and India, he added.

Paul Hunter, professor of medicine at the University of East Anglia, highlighted the latest UKHSA data suggesting hospitalizations were currently at stable levels and, although there had been a slight increase overall in positive cases , he stressed that an increase in infection was unlikely.

However, he added that while there was little evidence to suggest that FLiRT variants were inherently more infectious than previous dominant strains, they likely had a slight immune advantage – “and in a population with waning immunity, this is likely to contribute to the spread of the virus.