The Delta variant is already the dominant strain of Covid-19 in the United States, according to data modeling done by the US Centers for Disease Control and Prevention (CDC).
According to the health agency's estimates the Delta variant became dominant in the country over the two weeks ended July 3, with 51.7% cases linked to the variant that was first identified in India.
The proportion of cases linked to the Alpha variant which was first identified in Britain and had been dominant in the United States so far, fell to 28.7%.
The data, which shows the estimated biweekly proportions of the most common SARS-CoV-2 lineages circulating in the United States, is based on sequences collected through CDC's national genomic surveillance since Dec. 20, 2020.
The Delta variant, which is becoming dominant in many countries, is more easily transmitted than earlier versions of the coronavirus and may cause more severe disease, especially among younger people. It has now been found in every US state, health officials have said.
On Tuesday, US President Joe Biden encouraged Americans who have not yet been vaccinated against Covid-19 to get their shots to protect themselves from the widely spreading, highly contagious variant.
So far, preliminary data has shown that vaccines made by Pfizer Inc and BioNTech, AstraZeneca and Moderna are largely protective against Delta, with the concentration of virus-neutralizing antibodies being somewhat reduced.