After months of progress in slowing the spread of the virus that's killed over 600 thousand Americans, the United States is once again seeing cases, hospitalizations, and deaths rise stratospherically in the wake of the stronger, more contagious Delta variant.

Though nearly 200 million Americans have been vaccinated this year, there's still an insufficient number for herd immunity, where enough are vaccinated worldwide to limit the virus's ability to reproduce, thereby eradicating the threat of stronger, more vaccine-resistant variants like Delta becoming dominant.

As people around the world struggle to secure their vaccinations, millions of Americans have succumbed to right-wing disinformation regarding the vaccines, willfully refusing the opportunity to save not just their lives, but the lives of countless others. Until the number of fully vaccinated people reaches around 70 percent or higher, herd immunity will be unattainable.

Yet American resistance to vaccination appears to only grow stronger and more irrational, with claims that the vaccines are microchipped or act as the biblical "mark of the beast". Right-wing media personalities like those at Fox News and Newsmax seem determined to undermine public trust in vaccines whose safety and effectiveness has been repeatedly proven.

National Institute of Allergy and Infectious Diseases Director and top Biden Administration health advisor, Dr. Anthony Fauci, warned that—if vaccine-resistant Americans continue to refuse the vaccine—there is only one way to achieve herd immunity.

Watch below.

Fauci told MSNBC's Mehdi Hasan:

"The only way you could get to herd immunity without them is, the unfortunate situation, is if they all wind up getting infected, and then you'll have a combination of infected individuals who have some degree of protection, together with vaccinated individuals. But that's gonna lead to a whole lot of suffering, a whole lot of hospitalization, and a whole lot of death."

He added:

"We already have 620 some-odd thousand people who have already died in this country. We don't need anymore. We can get herd immunity really easily if you get everybody vaccinated."

The outlook is bleak.

There's growing frustration with the willfully unvaccinated and the risks they're imposing on Americans who did their part.

It's unclear when, or if, herd immunity will be reached, and Fauci doubts it will happen before next spring.