Delta-variant rates doubled in the US in 2 weeks, Fauci said: from 9.9% to 20.6%. It could derail the US COVID-19 recovery.

Dr Antony Fauci speaking at a press briefing on June 22. He is sitting in front of two flags and a background that has the NIH logo repeating
Dr. Anthony Fauci on June 22. The White House
  • The Delta variant is the “greatest threat” to US COVID-19 efforts, Dr. Anthony Fauci said Tuesday.
  • He said its prevalence in the US doubled within two weeks, a worrying sign.
  • The variant is more transmissible and dangerous than other types of the coronavirus.
  • See more stories on Insider’s business page.

The proportion of Delta-variant coronavirus cases in the US doubled in two weeks, Dr. Anthony Fauci said on Tuesday.

Speaking at a press briefing, Fauci, the White House chief medical advisor, said the variant was the “greatest threat” to the US efforts to eliminate COVID-19.

The Delta variant now makes up 20.6% of the COVID-19 cases in the US. That is about double the rate seen on June 5, when the variant made up 9.9% of cases.

On May 22, 2.7% of cases were caused by the Delta variant, Fauci said.

He said the US seemed to be “following the same pattern” as the UK, where the variant quickly became dominant and now makes up 99% of cases.

A screengrab of the press briefing on June 22 shows a graph of delta variant rates rising from 1.2% to 2.7% to (.9% to 20.6% every two weeks ending on June 19. Next to the graph, a woman is signing.
A graph citing CDC data that shows Delta-variant rates growing every two weeks, at a White House press briefing on June 22. The White House

In an interview with “Good Morning America” on Friday, Dr. Rochelle Walensky, the director of the Centers for Disease Control and Prevention, said the variant would likely become dominant in the US in the coming months.

On Monday, the World Health Organization called the Delta variant the “fittest” strain of the coronavirus yet.

That’s because – compared to the Alpha variant, which to date is still dominant in the US – the Delta variant is a lot more transmissible.

It also appears to cause more hospitalizations and seems more likely to break through the protection given by one dose of the Pfizer and AstraZeneca vaccines.

Two doses of those vaccine are still effective at preventing symptomatic disease.

It’s unclear how much protection the Moderna and Johnson & Johnson vaccines give against the variant.

On Friday, President Joe Biden urged Americans to get fully vaccinated.

He said young adults are particularly vulnerable as they are less likely to be vaccinated and more likely to be socializing than older people.