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XBB.1.5 COVID mutation dominant in South Florida, but immunity keeps worst at bay

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Although reported cases are trending down in Florida, the coronavirus that causes COVID-19 continues to mutate. The latest subvariant, called XBB.1.5, has mutations that make it highly transmissible and somewhat resistant to vaccines and past infection.

Although recent case counts have trended down, a more contagious subvariant of the coronavirus that causes COVID-19 is spreading quickly in South Florida and is becoming the dominant one in the country.

In the week ending on Jan. 21, this subvariant of omicron, called XBB.1.5, made up 39% of cases in a region of the U.S. that includes Florida, Georgia, Mississippi, North and South Carolina and Tennessee, according to the U.S. Centers for Disease Control and Prevention.

The spike protein of this subvariant has a mutation — or change in the spike — called F486P, that lets it attach to human cells more easily and get in, spreading the virus.

“That's the reason we're seeing more and more of it," said Aileen Marty, an infectious diseases expert at Florida International University.

This subvariant of the SARS-CoV-2 virus, which causes COVID-19, is not weaker than others. But people aren't experiencing terrible severity in side effects because of immunity across our population.

"Omicron is a really bad virus, but we have built up immunity in our population because we've had such a high rate of infection," Marty said. "People with hybrid immunity have far better immunity than people who only have infection and never got the vaccine. That’s not a good choice, and hybrid immunity turns out also to be better than just the vaccine.”

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On Jan. 19, 2023

Marty said the oral antiviral called Paxlovid is quite effective in keeping patients out of the hospital, whereas monoclonal antibodies currently available are not effective against most of the circulating variants, she added. If the U.S. did more genetic sequencing of coronavirus variants, doctors would know which infection their patients have and that way know better what to prescribe.

The experience of adults with this variant seems similar among children. Nicklaus Children's Hospital in Miami is not seeing an uptick in children coming in with bad cases of COVID-19, said Dr. Marcos Mestre, vice president and chief medical officer.

Some children "have been infected, have had vaccines, have had some degree of booster, so we haven’t really seen much in terms of severity as we were seeing with other variants in the past,” Mestre said.

Verónica Zaragovia