The Delta coronavirus variant, which is highly transmissible and possibly more dangerous than current predominant variants, now makes up more than 20% of all samples sequenced in the United States after the percentage doubled in a recent two-week period, Dr. Anthony Fauci said.
The country seems to be following a pattern seen in the United Kingdom, both with a variant first seen there -- the B.1.1.7 Alpha -- and now with the Delta variant, said the director of the National Institute of Allergy and Infectious Diseases.
"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 Tuesday at a White House Covid-19 Task Force briefing.
Some labs genetically sequence samples of the virus taken from patients to find out which variant is involved, and these test results are reported to the US Centers for Disease Control and Prevention.
Offering some good news, Fauci said the mRNA vaccines, which are made by Pfizer/BioNTech and Moderna, appear to hold up against the Delta variant.
The Pfizer/BioNTech vaccine was 88% effective in preventing Covid-19 symptoms in the Delta variant two weeks after the second dose of the vaccine, he said.
"When you look at hospitalizations, again, both the Pfizer BioNTech and the Oxford AstraZeneca are between 92 and 96% effective against hospitalizations," Fauci said.
The challenge, though, is getting more people to take the vaccines.