rand fauci others clash

over the pandemic rules

>> pierre, thank you.

>>> we're going to turn now to the tension hearing on the hill today involving the back and forth between dr. anthony fauci and senator rand paul.

At one point, dr. fauci telling the nor, "you're not listening."

And the nation's top scientists with a reality of shorts, how soon there could be a potential vaccine here in the u.s. and how long it would take before all americans would have access to it.

Mary bruce up on the hill tonight.

>> reporter: as the nation marks a horrific milestone, 200,000 killed by the coronavirus, today, the head of the cdc dr. robert redfield with a stark reality check.

>> a majority of our nation, more than 90% of the population, remains susceptible.

>> reporter: on capitol hill, the nation's top health experts trying to convince americans to take a vaccine, when one becomes available.

Saying they themselves will.

>> i certainly would take that vaccine.

>> i would have no hesitancy to recommend to my family.

>> reporter: but a growing number of americans are skeptical, as the president sends mixed messages on the virus and amid growing concerns that his administration is putting politics ahead of science.

Today, the head of the fda insisting they can be trusted.

>> our thorough review processes and science will guide our decisions.

Fda will not permit any pressure from anyone to change that.

I will fight for science.

>> reporter: but even in today's hearing, the scientists faced pushback.

Republican senator rand paul trying to discredit anthony fauci, questioning why new york has beaten back the virus.

>> they are looking at the guidelines that we have put together from the task force of the four or five things of masks, social distancing, outdoors more than indoors, avoiding crowds and washing hands.

>> or they've developed enough community immunity that they're no longer having the pandemic because they have enough immunity in new york city to actually stop.

>> i challenge that, senator.

>> i'm afraid -- >> please, sir, i would like to be able to do this because this happens with senator rand all the time.

You are not listening to what the director of the cdc said, that in new york it's about 22%.

If you believe 22% is herd immunity, i believe you're alone in that.

>> reporter: the president has said a vaccine will be ready as early as next month, just before election day.

>> we're on track to deliver and distribute the vaccine in a very, very safe and effective manner.

We think we can start sometime in october.

>> reporter: trump even taking on his own cdc director last week, when redfield predicted americans won't be able to take advantage of a vaccine until mid-2021.

>> i think he made a mistake when he said that.

It's just incorrect information.

>> reporter: today, he was asked if he's under political pressure.

>> so, did you get any political push-back for saying what you said?

>> i stand by trying to present the data and the science as i see it and i will continue to do that.

>> reporter: redfield agrees with the president that a vaccine could be authorized by november but is making it clear it would not be widely available then.

>> i think that's going to take us to april, may, june, possibly july to get the entire american public completely vaccinated.

>> reporter: and fauci warning even then, covid isn't going to just disappear.

>> the vaccine availability will go a giant step to controlling the infection, but you're not going to completely eradicate or eliminate it.

>> tense moments on the hill today.

Let's get right to mary bruce on the hill tonight, because mary, there is also new developing involving a fourth potential vaccine, of course, this one from johnson & johnson, which is now starting its final stage of trial.

And i know if this vaccine is approved, this one would be actually different?

>> reporter: david, unlike the others, this vaccine would be just one shot.

The others would require two doses.

The company tells us this means they could treat twice as many americans.

It is now entering these final trials and the first batch could become available early next year.