California COVID cases and hospitalizations are surging again

California is seeing a sustained rise in
cases and hospitalizations, with numbers climbing at the same alarming rate that the state experienced ahead of previous COVID-19 surges.

Nearly a year to the day the
first case of the omicron
variant in the United States was identified in a San Francisco resident, the daily number of newly reported cases in the state has climbed to 5,466, up 157% from a month earlier. More worryingly, new hospital admissions of patients with confirmed COVID are at 3,793, up 133% over the same period, according to
health department data
published Thursday.

With the third holiday season since the start of the pandemic underway and colder weather driving people indoors amid laxer attitudes, public health experts are bracing for another virus wave this winter. Hospitals are
already under strain
from two other infectious diseases this year —
respiratory syncytial virus and the flu
— that have come back with a vengeance.

Bay Area public health experts say they can’t predict how bad things will get, given the high level of overall immunity in the population from vaccination or prior infection. But they are worried about the emergence of new omicron subvariants such as
BQ.1 and BQ.1.1
that evade immunity more successfully than earlier strains, even as disappointingly small numbers of people have gotten the latest COVID vaccine booster shots.

“I think the holiday season is going to be a fertile ground for COVID to spread, a fertile ground for influenza to spread,” said Dr. Warner Greene, a senior investigator with the Gladstone Institutes. “I think we can expect to see both viruses increase. And so I think if you’re in those high-risk strata, you need to be very proactive and take strong steps to protect yourself.”

The number of people hospitalized with confirmed COVID-19 across the state as of Thursday marked the highest figure since the summer wave in August, while available intensive care unit beds have fallen below 1,900 for the first time since March.

The state’s seven-day rolling test positivity rate, which tracks the percentage of lab test results that are positive for COVID-19, has also topped 10% — more than doubling in a month.

“It’s hard to know where we are right now,” said Dr. John Swartzberg, a UC Berkeley infectious disease expert. “Things aren’t quite going in the right direction — they’re going in the wrong direction.”

The rapid spread of the immune-evasive subvariants adds to the concern. Together, the BQ.1 and BQ.1.1 offshoots drove nearly 6 in 10 new infections in the U.S. last week, according to the U.S. Centers for Disease Control and Prevention. The agency has also started tracking the
omicron XBB coronavirus subvariant, which
drove surges across Asia
this fall.

“There will almost certainly be a seasonal surge in the virus,” said Greene. “The dimensions of that are unclear. If XBB takes over, this is the most immune-evasive variant. It is now doubling in the United States at a rate of every 12 days. And one kind of suggests that it may push BQ.1 and BQ.1.1 aside. In that case, that is a highly, highly infectious virus and the boosters are not as effective.”

California’s seven-day average has reached about 13.6 new cases per 100,000 people, with the Bay Area region reporting roughly the same figure. That’s nearly twice the daily case rate at this time
last year, which hovered at 7.8 per 100,000 people and ranged from 5.8 to 10 cases per 100,000 across the nine counties.

COVID-19 hospitalizations in the Bay Area are up 87% since October, reflecting a nationwide trend since the Thanksgiving weekend. The overall seven-day average of new daily admissions in the U.S. for all age groups is up 18% from a week ago, according to
numbers updated overnight
by the CDC.

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“Two weeks from Thanksgiving, we’ll see what the Thanksgiving effect is,” said Swartzberg. “I think it’s going to probably accelerate — by how much I don’t know — but accelerate the number of cases and cause a rise in the number of hospitalizations.”

The agency’s
national ensemble forecast
predicts the number of new daily confirmed COVID-19 hospital admissions could rise as high as 11,000 patients on Dec. 23. California is likely to see up to 1,000 new admissions over the same period, based on
state-level forecasts.

Less than three months after the
updated bivalent boosters
against COVID-19 became available, the seven-day average of Americans getting the shots has fallen to 223,730 per day after peaking at 605,655 per day last month, according to data from the CDC. About 12% of all those eligible and 31% of those over 65 nationwide have gotten the new doses, which are formulated to target the original virus and the omicron variant offshoots.

“I think people hear that the boosters are less effective than the vaccine used to be, and for some people they say therefore why do I need to get it?” said Dr. Bob Wachter, chief of medicine at UCSF. “And the answer is, it’s less effective than it was at preventing infection, but still remains extremely effective at preventing severe infection.”

In California, just 16% of those eligible have gotten the bivalent booster.

“We got spoiled early on that the vaccines were quite good at preventing infections for several months,” Greene said. “Now, with those immune-evasive variants, those antibodies are not as effective and so the immunity provided against infection is more short-lived. It wanes more quickly. So it puts people at greater risk for infection.”

Aidin Vaziri and Matt Kawahara are San Francisco Chronicle staff writers. Email: