AMNA NAWAZ: The Centers for Disease Control and Prevention has changed its COVID guidance for when people need to isolate.

It's part of the CDC's broader recommendations on respiratory illnesses.

The agency now says people who've tested positive can return to normal activities when symptoms are improving and they have been fever-free for at least 24 hours without medication.

But the CDC also encourages people with improving symptoms to take additional prevention measures, like mask-wearing and keeping distance in public.

CDC Director Dr. Mandy Cohen joins me now.

Dr. Cohen, welcome back to the "NewsHour."

Thanks for joining us.

DR. MANDY COHEN, Director, Centers for Disease Control and Prevention: Thanks for having me.

Great to be here.

AMNA NAWAZ: So this is the first time you have shifted guidance, or isolation guidance, since 2021.

That was when it was reduced from 10 days to five days.

Why these changes in guidance right now?

What's that based on?

DR. MANDY COHEN: Well, we are in a different place.

And that's after a lot of hard work to make sure that we had the tools to protect each other against COVID.

What we have been seeing is lower hospitalizations and lower deaths, even as we saw high levels of virus spread.

So this past winter season, we saw both in our wastewater data and others that there was a lot of virus spreading in our community, but luckily those trends in hospitalizations and death continued to go down.

And what we were seeing is that really vaccination is what is continuing to protect folks.

So we wanted to unify our guidance today, not just for COVID, but across COVID, flu and RSV, so folks could have commonsense practical solutions that they could use every day that they can remember, that they can implement across a range of viruses.

AMNA NAWAZ: Now, there were some states, as you know, like California, Oregon, others that began relaxing their COVID isolation guidance as early as last year, counter to your guidance at the time.

Is this sort of the CDC kind of chasing, catching up to where people have already been for a while?

DR. MANDY COHEN: Well, you know what?

We were looking at this guidance last summer and seeing if we can move in this direction.

And then the virus changed in last August.

And we wanted to make sure we were through another winter season, that those trends in lower hospitalizations and lower deaths continued to hold.

And the good news is, they did.

And so we feel comfortable moving forward now.

But, remember, like always, this virus is changing.

If anything changes in terms of our effectiveness of vaccines or treatment, we may be back here needing to change guidance.

But we feel comfortable aligning across COVID, flu and RSV for some simple solutions, like vaccination, like making sure you get treatment and staying home when you're sick.

AMNA NAWAZ: Well, as you mentioned, the cases of COVID have fallen dramatically, but your data does show that there are still hundreds of people dying every week from COVID, still some 20,000 hospitalized weekly.

As you know, this guidance change has its critics.

Among them is Dr. Eric Topol, who co-authored one of the first reviews of asymptomatic COVID infections.

He said that this policy change is reckless.

And he said it will serve to promote more spread of COVID and long COVID.

Could it do that?

DR. MANDY COHEN: So, one, I want to say, remember, vaccines and treatment continue to protect folks.

Just this past season, in the beginning of the season, if we saw that 95 percent of the people who were coming to the hospital did not have an updated COVID vaccine, and 70 percent didn't have the one from the year before, right?

So what we're seeing, said another way, is, vaccines can protect us from going to the hospital or having our life being taken by this virus.

So we have to use those tools.

I think you also know that far too few adults got the updated COVID vaccine.

Only about 20, 22 percent of adults got the updated COVID vaccine, 40 percent of seniors.

So we definitely need to see folks using that important tool to protect themselves.

AMNA NAWAZ: But, to be fair, the vaccine can obviously prevent serious illness, but it doesn't prevent spread of COVID.

Will people isolating for a shorter amount of time potentially add to the spread of the virus?

DR. MANDY COHEN: Well, the good news is, when you get vaccinated, right, you are both less likely to go into the hospital, but you're also less likely to get long COVID, and you are less likely to get this virus overall, right?

So, less virus spreading means that we are protecting others.

And, now, we wanted to give simple, clear kinds of guidance, so that folks can remember them, it can be really actionable, because if more people are using the guidance, we think that's going to benefit everyone.

And, look, the folks who are vulnerable, they were top of mind for us at CDC as we were thinking about this guidance.

We all know someone who's at higher risk, over 65 or immunocompromised.

I have them in my own family.

So we were thinking about them as we did this guidance.

We think we found the balance to protecting the most vulnerable and having this clear and simple way for most folks to protect themselves.

AMNA NAWAZ: You also said this week that Americans 65 and older should get an additional dose of that latest COVID vaccine this spring.

Do you worry that relaxing the guidance at the same time you're asking people to go and get another booster sends conflicting messages?

DR. MANDY COHEN: No.

And, in fact, our guidance today, the very first core strategy that we want to emphasize to folks is about being up to date on your vaccines.

Vaccines is what we are continuing to see protect folks here.

So, we want to make sure folks are getting those updated vaccines.

And I want to preview for folks that we know this COVID virus continues to change, and we need to stay ahead of it.

And we have already started the process, CDC and FDA, to update the COVID vaccine for later this year.

So, right now, folks should start planning for this fall to get both an updated COVID vaccine and an updated flu shot.

AMNA NAWAZ: All right, Dr. Mandy Cohen, CDC director, thank you very much for joining us.

Good to speak with you.

DR. MANDY COHEN: Thank you so much.