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Delta Variant Surges In LA And More Vaccinated People Are Testing Positive

A chart displays current coronavirus cases in L.A. County. 2,767 were reported on July 22.
The number of COVID cases and the positivity rate both continue to climb in L.A. County.
(Courtesy L.A. County Dept. of Public Health)
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Coronavirus transmission continues to be “significant” in Los Angeles County, driven by the highly transmissible delta variant, public health officials reported Thursday.

“The overwhelming number of cases are among the unvaccinated” said L.A. County Public Health Director Barbara Ferrer.

A seven day average of daily COVID case rates shows a massive peak at the end of 2020 into early 2021, then a near flattening to zero with numbers going up again in July.
(Courtesy L.A. County Dept. of Public Health)

Case rates have been climbing at an alarming pace, increasing to 12.9 cases per 100,000 people, up from 7.4 a week ago.

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“The last time we saw case rises this quickly, as they are now, was back in early December of last year and that was during our very worst surge,” Ferrer said.

People under the age of 50 account for the vast majority of new cases. Older people are still more likely to be hospitalized, despite being the age group with the highest vaccination rate.

A line chart shows a peak in COVID hospitalizations between mid-November 2020 and mid-February 2021.
(Courtesy L.A. Dept. of Public Health)

Per capita cases are increasing the most in affluent areas of the county such as Beverly Hills, the Hollywood Hills and Studio City. Ferrer attributed it to personal behavior, as people have resumed seeing friends and going out.

“More people are intermingling as they're taking advantage of our full reopening,” Ferrer said. “If people are unvaccinated — and in all of our communities we have significant numbers of people still unvaccinated — that's where this virus is going to go.”

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Breakthrough Cases Going Up

There has also been a rise in fully-vaccinated people testing positive for the coronavirus, what are known as “breakthrough cases.”

One-in-five positive COVID-19 tests reported in June in L.A. County were among fully vaccinated people.

“[Delta] is by far the most infectious variant we’ve ever seen,” Ferrer said. “You end up with more breakthrough cases because it’s a more infectious variant.”

Breakthrough infections are up 58 percent since last week, but still make up a small portion of all cases.

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“Very few of them ended up hospitalized and an even smaller number ended up passing away,” Ferrer said.

A chart in the county's presentation listed 4,855,839 fully vaccinated people for the time period between January 19 and July 20. Of those, 6,520 had tested positive, 287 had been hospitalized and 30 had died. The rates for fully vaccinated people:

  • .13% tested positive
  • .0059% hospitalized for COVID
  • .0006% died
Editor's note
  • After initially publishing the chart that accompanied these statistics, LAist removed the image because did not accurately depict the size of each cohort.

The good news, according to Ferrer, is that all three coronavirus vaccines authorized in the U.S. offer strong protection against severe disease and death from COVID-19. But both shots are needed if you’re getting the two-dose vaccines made by Pfizer and Moderna.

A study published in the New England Journal of Medicine found that the Pfizer vaccine was 36 percent effective against symptomatic disease caused by the delta variant after the first shot, but jumps to 88 percent effective after the second shot.

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Nationally, there's no exact number of breakthrough cases. There is no way to count asymptomatic breakthrough cases, because the U.S. isn't testing nearly enough to catch them all. The CDC stopped keeping a running tally of mild breakthrough cases in May.

Bar chart shows percentage of new COVID cases attributed to vaccinated people. Feb: 0%. March 2%. April: 5%. May 11%. June 20%.
(Courtesy L.A. County Dept. of Public Health)

There has been a recent small uptick in vaccinations, but more than four million Angelenos are not yet vaccinated. That includes about 1.3 million children under 12 who are not eligible.

In response to the growing case numbers, last week county health officials announced that masks are again required indoors for everyone over the age of 2, even for fully vaccinated people. The move came a month after the statewide mask mandate, as well as most coronavirus restrictions, were rolled back on what was billed as California’s “reopening” by Gov. Gavin Newsom on June 15.

What questions do you have about vaccines?