The CDC is now classifying the delta COVID-19 variant, first detected in India, as a "variant of concern." The strain now accounts for nearly 10 percent of U.S. cases.
"This change is based on mounting evidence that the delta variant spreads more easily and causes more severe cases when compared to other variants, including B.1.1.7 (alpha,)" the CDC said in a June 15 statement shared with Becker's. "Two doses of the mRNA vaccine are effective against this variant and other variants currently circulating in the United States."
Research published June 14 in The Lancet found people infected with the delta variant have twice the risk of hospitalization compared to those infected with the alpha variant, which first emerged in the U.K. and is currently the dominant strain in the U.S.
The delta variant may become the dominant U.S. strain by fall, Scott Gottlieb, MD, former FDA commissioner and who serves on Pfizer's board of directors, told CBS News.
"It's doubling every two weeks," he said. "That doesn't mean that we're going to see a sharp uptick in infections, but it does mean that this is going to take over — and I think the risk is really to the fall that this could spike a new epidemic heading into the fall."
Pfizer's and AstraZeneca's COVID-19 vaccines have both recently demonstrated effectiveness at reducing the risk of infection and hospitalization in people with the delta variant. Pfizer's vaccine was 96 percent effective at preventing hospitalization from the variant, and AstraZeneca's was 92 percent effective.
The "variant of concern" designation is issued when there is evidence of increased transmissibility, more severe disease, or reduced effectiveness by treatments or vaccines, according to the CDC.