Washington, June 11 (RHC)-- The Director of the United States National Institute of Allergy and Infectious Diseases Anthony Fauci says the Delta coronavirus variant -- the B.1.617.2 variant first identified in India -- is still threatening to spread in the United States.

During a White House COVID-19 briefing, Fauci warned that spread of the Delta variant in the United Kingdom could be repeated in the US if people don't get vaccinated.  "We cannot let that happen in the United States, which is such a powerful argument to underscore what Dr. (Rochelle) Walensky said, to get vaccinated, particularly if you've had your first dose, make sure you get that second dose," Fauci said during a White House COVID-19 briefing.  "And for those who have been not vaccinated yet, please get vaccinated. This is the national month of action."

He also reiterated that the Delta variant "may be associated with an increased disease severity, such as hospitalization risk, compared to (the Alpha variant, B.1.1.7)."  Fauci, who is also an adviser to U.S. President Joe Biden, further claimed that a double dose of COVID-19 vaccine can be effective against the fast-spreading variant.

"There is reduced vaccine effectiveness in the one dose," said Fauci. "Three weeks after one dose, both vaccines, the (AstraZeneca) and the Pfizer/BioNTech, were only 33% effective against symptomatic disease from Delta."

The warning by Fauci comes as the pace of vaccinations across the US is falling, leaving unvaccinated Americans vulnerable to new variants.  Over the last week, the US averaged more than 1.07 million covid-19 vaccine shots administered per day -- well below the peak seven-day average of 3.38 million shots per day reached on April 13th, according to data from the CDC.