California Delta Variant Cases Now 83% Of Covid Infections Analyzed, Marking A 53% Rise In One Month


As he urged Californians to get vaccinated, Governor Gavin Newsom said twice this week that the share of analyzed positive Covid cases caused by the more transmissive Delta variant would be north of 60% when new numbers were announced. That’s up from about 53% in late July. The governor was underselling his point.

A monthly report on positive tests sent for genomic sequencing — which IDs specific variants — revealed that fully 82.8% of the positive tests analyzed were due to the Delta Variant. That’s a 53% rise in one month. And it’s up from Delta’s tiny 5.9% share of all variants in the state in May. See chart below.

According to CDC director Dr. Rochelle Walensky, California’s numbers mirror the national surge in Delta. The variant now makes up 83% of genetically sequenced cases nationwide, up from about 50% in early July, she said.

Federal and local officials say full vaccination still delivers highly effective protection against the Delta variant. A study published in the New England Journal of Medicine this week found the Pfizer vaccine to be about 88% effective against Delta, only a slight decrease from 94% efficacy against Alpha, California’s dominant variant earlier this year.

About 53% of all Californians are fully vaccinated, according to CDPH, while health leaders say the vast majority of hospitalized virus patients are unvaccinated.

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