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A Highly Contagious Covid-19 Variant Is Spreading in the U.S. What to Know. -- Barrons.com

Barron's · 01/06/2023 12:32
Josh Nathan-Kazis

Another highly contagious new Covid-19 variant is spreading rapidly across the U.S., raising concerns of a new wave of hospitalizations.

The variant, known as XBB.1.5, emerged as a major threat from among the goulash of variants circulating in the U.S. only in recent weeks, and significant questions remain about how much of a threat it poses.

What is clear is that XBB.1.5 is quickly pushing out other variants of the virus, and now accounts for the vast majority of Covid-19 cases in northeastern U.S., where hospitalizations are climbing quickly in some states.

A top World Health Organization Covid-19 official, Dr. Maria Van Kerkhove, told reporters on Wednesday that it is the most transmissible Omicron subvariant so far detected, but that whether it leads to more severe infections remains unknown.

"Our concern is how transmissible it is," Van Kerkhove said. "We do expect further waves of infection around the world, but that doesn't have to translate into further waves of death because our countermeasures continue to work."

There are no data yet on the severity of infections caused by XBB.1.5, Van Kerkhove said, but there is not yet any indication that their severity is any worse than that of other similar variants.

The variant, an Omicron descendant, accounted for over 40% of cases in the U.S. as of Dec. 31, according to the Centers for Disease Control and Prevention. That's up from 20% the prior week, and 10% the week before that.

Its share has grown quickly as it outcompetes the crop of strains that had pushed out BA.5 through the late fall.

Covid-19 hospitalizations are rising in the U.S., and are growing very quickly in parts of the northeast, where XBB.1.5 is most dominant. In the CDC region that covers New England, XBB.1.5 accounted for 75% of cases in the final week of 2022; hospitalizations in Connecticut are now up 27% over the past two weeks, while hospitalizations in Massachusetts are up 48%.

Van Kerkhove said that the WHO could not yet attribute the increase in hospitalizations in the northeastern U.S. to XBB.1.5. "We need to go deeper and look at the reasons for the increases in hospitalization and determine what is happening," she said.

The XBB.1.5 wave comes as the high rates in the U.S. of influenza and respiratory syncytial virus begin to recede. The CDC said that as of the final week of 2022, flu activity remained high, but was declining in most parts of the country. That could ease pressure on hospitals if Covid-19 hospitalizations continue to increase.

As is the case with other currently circulating variants, the monoclonal antibodies used as treatments in previous waves of the virus are not effective against XBB.1.5. Evusheld, AstraZeneca's (ticker: AZN) monoclonal antibody used to prevent Covid-19 in immunocompromised people, is also not effective against XBB.1.5. However, Paxlovid, Pfizer's (PFE) antiviral treatment, does remain effective, and current Covid-19 tests are also expected to work.

On Twitter on Wednesday, the White House Covid-19 Response Coordinator, Dr. Ashish Jha, argued that the severity of an XBB.1.5 wave would depend on " many factors," such as "immunity of the population, people's actions, etc." Jha urged people who had not received an updated bivalent booster to get one.

In a paper published recently in the journal Cell, Columbia University researchers wrote that the XBB family of variants demonstrate a "dramatically increased" ability to evade the immune system's neutralizing antibody responses, including in people who had received the updated bivalent mRNA boosters.

Even so, the vaccines are expected to provide protection against severe disease.

"Vaccination remains absolutely critical to preventing severe disease and death, no matter where you live," Van Kerkhove said.

Write to Josh Nathan-Kazis at josh.nathan-kazis@barrons.com

(END) Dow Jones Newswires

January 06, 2023 12:32 ET (17:32 GMT)

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