Delta variant expected to become dominant US strain, CDC says

The director of the U.S. Centers for Disease Control and Prevention said Friday that she expects the delta variant will become the dominant coronavirus strain in the United States and encouraged Americans to get vaccinated to be protected.

The delta variant, which was first detected earlier this year in India, has become dominant in Britain. The CDC also recently classified it as a "variant of concern," a designation that’s given when there is mounting evidence that the variant may spread more easily or cause more severe disease resulting in increased hospitalizations or deaths.

The delta variant now accounts for at least 10% of all U.S. COVID-19 cases, up from only 2.7% of cases on May 22. Some infectious disease experts have predicted that it could become the dominant strain as soon as this summer. 

But health officials, including CDC Director Rochelle Walensky, say the current vaccines being administered in the U.S. are proving effective against it.

"As worrisome as this delta strain is with regard to its hyper transmissibility, our vaccines work," Walensky told ABC’s "Good Morning America" on Friday. 

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FILE - Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention (CDC), testifies before a Senate Health, Education, Labor, and Pensions hearing to examine an update from federal officials on efforts to combat COVID-19 in the

She encouraged Americans to get fully vaccinated against COVID-19 and "you’ll be protected against this delta variant."

Hospitalizations in the U.S. have dramatically decreased this year with the administration of vaccines, dropping nearly 88% from the seven-day average peak in early January, CDC data shows. Some have even gone days without seeing any new COVID-19 patients. UNC Hospitals in North Carolina said its COVID-19 ICU ward went 36 hours without having a patient in early June, the first time in more than a year. 

Marin County hospitals in California also reported Monday that they didn’t have any hospitalized COVID-19 patients that day, also the first time in more than a year.

"The pattern couldn’t be clearer that vaccinations protect us," Marin County Public Health Officer Dr. Matt Willis said in a statement.

But with the noted progress, experts say the spread of the delta variant will pose a serious risk this summer to people who are not fully vaccinated. Dr. Ashish Jha, dean of Brown University’s School of Public Health, echoed that vaccination remains the best defense. 

"If you have not gotten vaccinated, this is a potentially very dangerous time because the Delta variant is spreading. It’s about 6% of infections in the United States right now, doubling every two weeks," Jha said June 15 on the "COVID: What Comes Next" podcast hosted by The Providence Journal. "If you do the math, in about four to six weeks we’ll start getting close to half… By mid-August, it’ll be the dominant variant in the United States."

To date, 65% of the U.S. adult population has received at least one dose of a COVID-19 vaccine and 55.2% of American adults are fully vaccinated. In total, 44.5% of the population, including those under 18, are fully vaccinated, CDC data shows

This story was reported from Cincinnati. The Associated Press contributed.