People who do not get vaccinated against the coronavirus, according to Anthony Fauci, increase the likelihood of Delta variant surges across the country.

In an interview with NBC's "Meet the Press" Sunday, Fauci, the nation's leading coronavirus expert, said the Delta variant might rise in different places even as overall vaccination rates increase and new Covid-19 cases decrease.

There's a "disparity in the willingness to be vaccinated," Fauci said. "So there are some states where the level of vaccination of individuals is 35% or less. Under those circumstances, you might expect to see spikes in certain regions, in certain states, cities or counties."

The Biden administration continues to laud the success of its vaccination initiative, saying that by July 1, 66.8% of U.S. adults and 54.6% of all Americans have received at least one dose.

However, the goal of 70% of adults having at least one shot by July 4 was missed. The government planned to host a Fourth of July party at the White House Sunday, with close to a thousand attendees.

Guests who had not been vaccinated were told they needed to wear a mask - but there was no such requirement. Mandates have also been repealed in states with low vaccination rates.

The Delta variant has been found in all 50 states, and health officials across the country are urging Americans to get vaccinated against the virus.

Delta has wreaked havoc on five states in particular: Arkansas, Colorado, Missouri, Nevada and Utah.

Specific counties in several states have a significantly higher incidence of confirmed coronavirus cases. The Delta variant, according to local health officials, is to blame for the rise.

According to the most recent data provided by Johns Hopkins University, more than 605,000 people in the U.S. have died as a result of the virus. About 47% of the total US population is fully vaccinated against the coronavirus, JHU data says.