The highly transmissible Delta strain has overtaken the Alpha variant to become the dominant variant in the US, according to new estimates from the US Centers for Disease Control and Prevention (CDC).
Delta, which was first found in India and is now in over 100 countries, represented 51.7 per cent of new infections in the US over the two weeks ending July 3, Xinhua news agency reported citing the CDC.
Meanwhile, the proportion of new cases caused by Alpha, which was first detected in Britain, was just 28.7 per cent over the same time period, according to the CDC.
Recently, health officials and experts have warned that the Delta variant was on track to become the dominant variant in the US, as its prevalence in the nation doubles about every two weeks.
They are concerned the variant will cause a surge in new cases this fall, hitting the unvaccinated population the hardest.
Increasing cases were reported in states with lower vaccination rates, including Alabama, Arkansas, Louisiana and Mississippi, according to the CDC.
Although Delta is highly contagious, research show that most vaccines still remain highly effective at preventing hospitalizations and deaths caused by the variant.
US President Joe Biden on Tuesday pushed for all eligible Americans to get Covid-19 vaccinations, stressing the importance of being protected against Delta.
The country reached its highest vaccination rate in mid-April when the seven-day average of doses administered daily topped about 3.4 million. But the rate has dropped since then.
About 47.6 per cent of the US population is fully vaccinated against Covid-19, and 55.1 per cent of the population has received at least one shot as of Wednesday, CDC data show.
Biden set a goal in May of having 70 per cent of American adults receive at least one Covid-19 shot by the Fourth of July. But just 18 states and Washington, DC surpassed that goal by the date, according to a Forbes report.