Coronavirus California

Here's how far doctors say delta variant sets back California's herd immunity

"I think we're going to have to go down the rabbit hole of wearing masks for the next few months," a UCSF doctor said.

ByStephanie Sierra KGO logo

Thursday, July 22, 2021

Herd immunity delayed? Here's how far doctors say CA is set backDoctors say the Delta variant is delaying California's timeline to reach herd immunity.

SAN FRANCISCO -- The highly-contagious Delta variant is pushing back the state's timeline to reach herd immunity, according to doctors at UCSF.

"I think it's going to get worse before it gets better," said UCSF Epidemiologist Dr. George Rutherford.

Dr. Bob Wachter, the chair of UCSF's Department of Medicine, tweeted out Tuesday the "#Delta variant has changed what it'll take to reach herd immunity" - adding we need more vaccinations and mask-wearing.

Rutherford predicts the state won't reach herd immunity for at least several months as case rates and hospitalizations are climbing rapidly across California.

"I'm guessing we have to be in the mid-80th percentile and that's not of people eligible for the vaccine, that's everybody, including children," he said.

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According to ABC7's vaccine tracker, 53 percent of the state's total population is fully vaccinated.

San Francisco County is at 69 percent fully vaccinated - one of the highest rates in the country. Yet, COVID cases are climbing at a pace health officials haven't seen since the onset of the city's last surge.

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"We've increased 8 fold in the past few weeks and we are projecting to be averaging 80 new cases per day," said San Francisco County Health Officer Dr. Susan Philip. "We were down in the low teens just a few weeks ago."

That pattern is seen across the Bay Area.

ABC7's data analysis found in the past month from June 20 to July 20 -- there have been hundreds of new COVID hospitalizations and more than a hundred new COVID ICU admissions collectively reported across all nine Bay Area counties.

Note: According to state data, a majority of the new cases stemmed in Sonoma County, but ABC7 has since been notified the state's data dashboard is outdated. ABC7 has reached out to CDPH for further clarification. In the meantime, our current totals don't include Sonoma County.

Contra Costa, Alameda, and Santa Clara counties reported the next highest totals, averaging anywhere between 30 to 60 new monthly hospitalizations. Most county figures are at least double the totals reported last month.

"I think the worst of it will come sometime in the fall, September or October," Rutherford said. "I think we're going to have to go down the rabbit hole of wearing masks for the next few months."

The only factors that could help speed up that extended timeline to reach herd immunity stems around how quickly the state can increase the pace of vaccinations of 13 to 17-year-olds. Not to mention, the added boost that will come after the shot is authorized for five to 11-year-olds.

"Both of those groups could really help us get to where we need to be," said Rutherford. "But, people need to be really cautious right now."

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