The nation’s leading infectious disease expert Dr. Anthony Fauci has a dire warning for those Americans who are not currently vaccinated as the Delta variant of the COVID-19 virus spreads across the U.S.

In an interview with PBS’ Judy Woodruff on Tuesday evening, Fauci cautioned that the Delta variant was a “game changer” for unvaccinated Americans and that it could cause“mini surges” in parts of the country where there are large populations of people who have not receive the COVID vaccine.

The Delta variant, which was first identified in India, has seen positive cases surging in states such as Missouri, Colorado, Mississippi, Alabama, and Arkansas. Former Food and Drug Administration commissioner Dr. Scott Gottlieb told CBS News’ “Face the Nation” on June 20.

Fauci told Woodruff, “It's the concern about unvaccinated people. So, if ever there was what I would say a clarion call to people to please get vaccinated, you can protect yourself against a virus that has a better capability of spreading from person to person and that could make you more seriously ill."

He continued by saying, “So that's the issue. You don't want to see two Americas, one that's protected very nicely because the vaccines work, and then certain pockets of the country where you can have these mini-surges which could really be very disconcerting and dangerous.”

Fauci maintained that with about 50% of the adult population fully vaccinated, and 66-67% of the adult population having received at least one dose of the COVID vaccine, “as a country, we’re doing very well.”

He said: “That's the good news, is that, if you are vaccinated, in general, you are doing fine.”

But the Delta variant poses a serious concern, as it currently accounts for 20% of COVID cases in the U.S., Fauci previously told CNBC.

“It is clearly more transmissible by multifold, a few times more,” he told Woodruff. He added that there is also more of a likelihood of getting hospitalized if infected with the Delta variant as compared to other variants of the virus.

“In certain countries, the Delta variant has become really quite dominant. It has pushed aside the other variants that are there. This will happen in our country, the United States, in those areas of unvaccinated people,” he told Woodruff.

“And, again, that's the reason why we say we're dealing with something we have to take very seriously. It's really a dichotomy. If you're vaccinated, you're in reasonably good shape, in fact, quite good shape. If you're not vaccinated, you're at significant risk.”

But Fauci was clear that no vaccine is 100%, saying that “we know that even the good vaccines, the ones that we really do know protect, protect about 88% against infection that's symptomatic and over 90% against severe infection.”

However, Fauci pleaded with Americans to get the COVID vaccine, telling Woodruff in the interview, “ Please, for your own safety, for the safety of your family, and for your communal responsibility to get this virus crushed, you do that when you get the overwhelming proportion of the population vaccinated."

He added, “So, I encourage very strongly people who are hesitant to get vaccinated to please get vaccinated.”

Top US pandemic advisor Anthony Fauci expects a decision on the J&J vaccine by American regulators by Friday Top U.S. pandemic advisor Anthony Fauci. Photo: POOL / Amr Alfiky