PPE is Back: Delta Variant Makes Up 83% Of New US Coronavirus Cases

(CNN)The more contagious Delta variant of Covid-19 now makes up 83% of sequenced samples in the United States, US Centers for Disease Control and Prevention Director Dr. Rochelle Walensky said Tuesday. 

"This is a dramatic increase, up from 50% for the week of July 3," Walensky said in a Senate committee hearing.

Health experts have said the Delta variant is more transmissible than any other identified variant so far. "We should think about the Delta variant as the 2020 version of Covid-19 on steroids," Andy Slavitt, a former senior adviser to Joe Biden's Covid Response Team, told CNN last week.

"It's twice as infectious," Slavitt said. "Fortunately, unlike 2020, we actually have a tool that stops the Delta variant in its tracks: It's called vaccine."

The most recent data from Israel evaluating effectiveness of the Pfizer/BionTech mRNA vaccine against the Delta variant found the vaccine to be 64% protective against infection, and that the vaccine is 93% effective in preventing severe disease and hospitalizations. 

Other studies indicate that the Moderna and Johnson & Johnson vaccines are also effective against the Delta variant.

The average of new daily cases this week is up 66% from last week and 145% from two weeks ago, as cases surge in 44 states, according to data from Johns Hopkins University. In addition, hospitalizations are up 26% from last week.

And 99.5% of deaths are among the unvaccinated, US Surgeon General Dr. Vivek Murthy told CNN's Dana Bash on "State of the Union" on Sunday -- a figure cited by the US Centers for Disease Control and Prevention earlier in the month.