A highly transmissible coronavirus variant and likely a more dangerous one than the presently predominant variants - the Delta variant -  now constitutes over 20% of all samples sequenced in the United States, said Dr. Anthony Fauci.

It appears that the U.S. is following the pattern that has been observed in the United Kingdom, stated Fauci. 

He added that the mRNA vaccines, developed by Pfizer/BioNTech and Moderna, seem to work against the Delta variant. The Pfizer/BioNTech vaccine has been shown to be 88% effective in preventing COVID-19 symptoms in the Delta variant two weeks following the second dose. Fauci further stated that both the Pfizer/BioNTech and the Oxford AstraZeneca vaccines are about 92 to 96% effective against hospitalizations… (CNN, June 23, 2021)