A rapidly spreading covid variant is highly contagious and can cause breakthrough infections, but it’s not more severe or dangerous than prior strains, local experts say.
The omicron subvariant — known as BA.5 — has “really taken off, nationally and locally,” said Dr. Lee Harrison, professor of infectious disease and epidemiology at the University of Pittsburgh.
“It is very, very infectious,” Harrison said. “There’s no doubt about it. In terms of immunity, it looks like even if you’ve had the previous omicron variants, there are enough differences in the BA.5 that you can get reinfected pretty easily.”
Nationally, the subvariant accounted for about 54% of sequenced strains, according to Centers for Disease Control and Prevention data, Harrison said. The related BA.4 subvariant constituted about 17% of sequenced strains.
“We’re seeing something very similar to the national trends,” Harrison said. “In Allegheny County, we’ve seen a very rapid increase recently in BA.4 and BA.5, with BA.5 being much more prevalent.”
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CDC data from the week ending July 2 indicates that BA.4 and BA.5 constituted about 59% of cases in the region, he said, and the majority of those were BA.5.
The new covid strain is the latest in a string of variants and subvariants that have emerged since the onset of the pandemic, said Dr. Amesh Adalja, a Pittsburgh-based infectious disease expert and senior scholar at the Johns Hopkins Center for Health Security.
This BA.5 subvariant is “very similar” to the BA.4 subvariant, he said, but “clearly different” from earlier versions of the omicron variant.
As new subvariants have emerged, they’ve become more contagious, said Dr. Tom Walsh, an infectious disease specialist for Allegheny Health Network. The BA.5 subvariant, Walsh explained, is “a little more contagious and a little more immune-evasive,” meaning it’s more likely to cause breakthrough infections — or cases of covid-19 in fully vaccinated individuals.
The disease is now “approaching measles” in terms of how contagious it is, he said of BA.5.
Despite the contagious and immune-evasive nature of the variant, experts said fully vaccinated individuals are still likely safe from the worst outcomes.
“The vaccines are extremely effective when it comes to prevention of serious illness, hospitalization and death,” Adalja said.
Hospitalization numbers “are going up slightly,” Harrison said, but death numbers “are staying relatively flat.”
“What’s happened is the nature of people being admitted to the hospital has changed from earlier in the pandemic,” he said. “So, if they get hospitalized, they tend to be less severe than earlier on. Hospitalizations are going up, because we’re seeing a large number of infections. We still see very severe cases and we still see deaths, but compared to earlier in the pandemic, the severity in the hospital has shifted to being less severe.”
Most people admitted to Allegheny Health Network hospitals with the virus are either unvaccinated or they’re elderly with multiple health problems, Walsh said.
Inpatient and outpatient therapeutics that treat covid-19 are still effective against the latest subvariants, he said, and the same basic mitigation strategies that have been highlighted since the onset of the pandemic can still reduce risk of infection.
In general, Walsh said, omicron infections seem to cause “less severe disease” than prior variants.
Vaccine manufacturers are working to produce new vaccines that may be more effective against omicron and other variants, Walsh said. But creating a vaccine specifically targeting the variant that is currently dominant can be tricky, he said, as variants change so rapidly that a new variant could be taking over by the time that vaccine is ready to be administered.
The BA.5 subvariant won’t be the last new variant or subvariant of the coronavirus, Adalja said.
“BA.5 is the dominant strain of the virus right now. It will eventually get supplanted by something else,” he said. “There’s going to be one after this and one after that, too. That’s what the virus is going to do — it’s going to evolve to continue to be able to infect us.”
That’s why researchers are working on pan-coronavirus vaccines that would target “all of the variants and subvariants” and provide immunity for ever-mutating strains of the virus, Walsh said.
It’s unclear when updated vaccinations may be available, Walsh said, though some experts have suggested as early as this fall.
Already, a new variant is cropping up overseas. Scientists say the variant — called BA.2.75 — may be able to spread rapidly and get around immunity from vaccines and previous infection, according to The Associated Press. It’s unclear whether it could cause more serious disease than other omicron variants, including the globally prominent BA.5.
Julia Felton is a Tribune-Review staff writer. You can contact Julia at 724-226-7724, jfelton@triblive.com or via Twitter .