Delta coronavirus variant doubling biweekly, now 20% of samples, Fauci says

Dr. Anthony Fauci warned Tuesday that the highly transmissible Delta variant has climbed to now account for over 20% of sequenced samples.

The variant, first detected in India and now found in over 80 countries, is becoming the dominant strain worldwide, according to the World Health Organization. The B.1.617.2 strain spreads more readily than the B.1.1.7 Alpha variant and the wild-type virus, and has been linked to an increased hospitalization risk.

"We seem, as was the case with B.1.1.7, we seem to be following the pattern with the Delta variant, with a doubling time of about two weeks," Fauci said during a White House COVID-19 briefing Tuesday, citing CDC data suggesting the Delta variant was behind 1.2% of sequenced samples on May 8, before climbing to 2.7% on May 22, 9.9% on June 5 and increased to 20.6% by June 19.

However, the authorized vaccines appear to remain effective against the variant, with the Pfizer vaccine demonstrating an 88% efficacy against symptomatic disease two weeks post-second dose. A study out of the U.K. found Pfizer’s vaccine was 96% effective against hospitalization from the Delta variant following two doses, and the Oxford-AstraZeneca vaccine (not yet approved in the U.S.) was 92% effective against hospitalization from the Delta variant after two doses.

"Similar to the situation in the U.K., the Delta variant is currently the greatest threat in the U.S. to our attempt to eliminate COVID-19," Fauci said. "Good news, our vaccines are effective against the Delta variant."

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