IE 11 is not supported. For an optimal experience visit our site on another browser.

The delta variant is now the dominant Covid strain in the U.S.

The highly transmissible variant now accounts for more than 50 percent of new Covid-19 cases.

The highly transmissible delta variant is now the dominant strain of the coronavirus in the United States, the Centers for Disease Control and Prevention reported Tuesday.

As of July 3, the latest date for which data was available, the delta variant accounted for 51.7 percent of new Covid-19 cases that had been genetically sequenced in the country. Two weeks earlier, on June 19, the variant accounted for just over 30 percent of new cases.

Full coverage of the coronavirus outbreak

During a news briefing Tuesday, President Joe Biden cited the delta variant's rapid spread to urge people to get vaccinated, "especially young people who may have thought that they didn't have to be vaccinated, didn't have to worry about it, didn't have to do anything about it."

"This should cause everybody to think twice," Biden said.

Studies have shown that the Covid-19 vaccines are effective against multiple variants, including the delta variant. A recent report from Public Health England, where the variant accounts for more than 90 percent of new cases, found two doses of the Pfizer vaccine to be 96 percent effective against hospitalization.

Download the NBC News app for full coverage of the coronavirus outbreak

In addition to the U.S., the delta variant has been detected in 103 countries and is predicted to become the dominant variant globally.

"Based on the estimated transmission advantage of the delta variant, it is expected that delta will rapidly outcompete other variants and become the dominant circulating lineage over the coming months," the World Health Organization said Tuesday.

Worldwide, the number of new Covid-19 cases has increased slightly over the past two weeks, after a seven-week decline, according to the WHO. Covid-19-related deaths, however, continued to decline, reaching the lowest point since October 2020.

Follow NBC HEALTH on Twitter & Facebook.