Delta variant now makes up 83% of cases, CDC director says

Rochelle Walensky, director of the U.S. Centers for Disease Control and Prevention (CDC), attends a Senate Health, Education, Labor, and Pensions Committee hearing at the Dirksen Senate Office Building in Washington, D.C., July 20, 2021.
[ – 2021.07.20] Centers for Disease Control and Prevention Director Rochelle Walensky told lawmakers Tuesday the delta variant now makes up 83% of cases, up from 50% at the beginning of this month.

“CDC has released estimates of variants across the country and predicted the delta variant now represents 83% of sequenced cases. This is a dramatic increase from — up from 50% for the week of July 3rd,” she testified in a hearing before the Senate Health Committee.

Walensky said the alarming increase was happening the most in unvaccinated areas and that they were “allowing for the emergence and rapid spread of the highly transmissible delta variant.”

“In some parts of the country, the percentage is even higher, particularly in areas of low vaccination rates,” she said.

The best way to stop the spread is with vaccines, she said.


And on the subject of whether booster shots — which could offer extra protection against the variant for immunocompromised people — will be recommended, Walensky and Food and Drug Administration acting chief Janet Woodcock said they don’t yet have a timeline on an answer.

They were pushed multiple times by Republicans who argued Israel has already made the call to use boosters.

Although the nation’s COVID officials would not give a timeline on when Americans will need boosters, they detailed what they’re looking for to make that decision.

Immunity will slowly decrease, not unexpectedly plummet, the top COVID experts said, and when vaccines get around 70-80% efficacy, boosters will be necessary.

“Fortunately, we’re anticipating that this will wane and not plummet so as we see that waning, that will be our time for action,” Walensky said.

Walensky said the CDC is following a handful of groups, including thousands of people in nursing homes, health care workers, and essential workers, testing them weekly. The CDC is also doing lab studies.

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