Omicron BA.5 strain may shorten COVID immunity from 3 months to 28 days, research shows

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Wednesday, July 13, 2022
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New research shows the latest highly-transmissible COVID-19 omicron subvariants BA.4 and BA.5 may be shortening the window of immunity post-infection.

SAN FRANCISCO (KGO) -- New research shows the latest highly-transmissible COVID subvariants may be shortening the window of immunity post-infection.

"I think this is a wake-up call," said UCSF's Dr. George Rutherford. "For all of us."

The warning comes from Australian health officials who say the BA.4 and BA.5 strains are so strong at evading antibodies -- they're seeing COVID reinfections happen faster and more frequently compared to other variants.

"This means your period of immunologic protection following infection is probably shorter," Rutherford said. "We previously thought it was around three to four months. It's probably less."

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How much less? A committee of Australian doctors are changing recommendations to reduce the definition of immunity from 90 days to 28 days.

"Do you think we should do the same?" ABC7's Stephanie Sierra asked.

"It's something up for discussion," said Rutherford, who specializes in infectious diseases. "If you were infected at the beginning of the summer, there's nothing saying you can't be infected again today with one of these newer variants."

The omicron subvariant BA.5 is now the most dominant strain in the U.S. accounting for roughly 65% of new cases, according to ABC's analysis of federal data. BA.4 accounts for 16%. The two combined are dominating the latest surge - making up more than 80% of new cases nationwide. And the reality is, those figures are likely much higher.

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"We're probably seeing just a drop in the bucket in terms of official cases," said UCSF Infectious Disease Physician, Dr. Peter Chin-Hong.

As most of the Bay Area braces for another surge, Solano County is already in one.

"It's already here," said Dr. Bela Matyas, Solano County's Health Officer. "We've seen it. We've seen a bump in our cases, 10 to 15%, about 30 per day more over the past week than we did prior."

Every Bay Area county is reporting an increase in hospitalizations, but the uptick is not currently overwhelming hospital systems. The areas reporting a steady increase in new hospital admissions over the past week include: Marin, Napa, Contra Costa, Alameda, Santa Clara, and Solano counties. But thankfully, these counties aren't seeing any major impacts to ICU admissions.

CORONAVIRUS DATA: Updated number of COVID-19 cases, deaths in San Francisco Bay Area

"So the good news, while BA.4 and BA.5 are more transmissible it seems so far to be much less severe," said Matyas. "Most patients aren't getting severely sick."

Some have raised the question -- could change if someone is infected with both strains?

"You can be infected with more than one virus at the same time... for any disease," Rutherford said. "That's totally possible. So it may happen, but I expect it's a pretty rare occurrence."

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