The CENTERS for Disease Control and Prevention reported Tuesday that the highly transmitted delta variant is now the dominant strain of coronavirus in the United States.

As of 3 July, the latest date for which data are available, the Delta variant accounted for 51.7 per cent of new COVID-19 cases that had been genetically sequenced in the country. Two weeks ago, on 19 June, the variant accounted for just over 30 per cent of new cases.

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At a press conference on Tuesday, President Joe Biden cited the rapid spread of the Delta variant to urge people to get vaccinated, "especially young people who may think they don't have to get vaccinated, don't have to worry, don't have to do anything about it."

"It should make everyone think twice," Mr. Biden said.

Studies have shown that the COVID-19 vaccine is effective against a number of variants, including delta. A recent report by Public Health England found that the mutation accounted for more than 90 per cent of new cases and found that two doses of Pfizer's vaccine were 96 per cent effective against hospital treatment.