Epidemiologist at the University of Alabama at Birmingham School of Public Health Suzanne Judd, Ph.D. joins Yahoo Finance’s Akiko Fujita to discuss how the CDC reduced the number consecutive minutes of COVID-19 exposure needed to be a 'close contact’.

Video Transcript

AKIKO FUJITA: Well shares of Moderna are climbing in this session, that stock up nearly 4% on news it has completed the enrollment of that phase III study for its coronavirus vaccine. The drug maker saying more than 25,650 participants have received the second vaccination. All of this coming as we continue to see the uptick in COVID cases, for now seeing 60,000 new cases per day here in the US.

Let's bring in Dr. Suzanne Judd. She is an epidemiologist at the University of Alabama at Birmingham School of Public Health. And Dr. Judd, let-- put this in context for us. You know, we get all these headlines on the vaccine from-- on a daily basis. Moderna specifically, we did hear from the CEO earlier this week saying he expects to get FDA authorization in December if things look good in November. How should we be looking at these headlines coming out of the company today?

SUZANNE JUDD: It's promising. It's promising that they have enrolled everyone they wanted to enroll. It's still not a short-term when. There are a lot-- there's a lot that goes into getting a vaccine. They have to manufacture it. They have to get enough of the vials so that they can actually administer it to large portions of the population, and that just doesn't happen overnight. So approval is one step, but approval doesn't mean that the pandemic's over.

AKIKO FUJITA: In the absence of the vaccine though we are continuing to see those case counts tick higher. What are you seeing on the ground there in Alabama?

SUZANNE JUDD: Cases are going up here as well, particularly in young people. The schools have opened, so there's a lot of transmission happening from younger siblings that are in the house and then getting parents and older siblings that may be off at college-- are also getting sick. The silver lining is that the deaths and hospitalizations haven't been as high, so we're experiencing lower mortality rates than we saw earlier this year, which could be due to better medical management with COVID. Or it could be that there's a seasonal effect that when you get COVID in the late summer, early fall, perhaps it's not as severe as if you were to get it in the winter, which we do see with influenza, too.

AKIKO FUJITA: What's the science behind that? Why is it not as bad in the fall?

SUZANNE JUDD: Typically there's great argument the scientific community, but a lot of people think it has to do with vitamin D. Vitamin D-- windows are open, so air is being exchanged at higher rates for-- as it's coming in and out of the house. One of those two reasons typically are the reasons people point to why the rates are lower in the fall.

AKIKO FUJITA: You just mentioned the concerns about spread in schools. We got new CDC guidelines sort of shifting the argument on who exactly will be considered a close contact. It used to be those who were within six feet in 15 consecutive minutes. The CDC has now said if there is contact within 15 minutes over a 24-hour period that would be considered a close contact. How does this shift the planning for schools or offices who have been operating on the CDC guideline?

SUZANNE JUDD: It becomes incredibly complicated. I'm not actually sure how a school will begin to operationalize it, or even a workplace. What this means is that you have to guess who you came in contact with at various time points. These are the passing conversations in the hallway, at the drinking fountain, at the coffee pot, in the bathroom. Before you had to be in the room for 15 consecutive minutes with the person. Now you can just pass by them.

So it's a bit confusing, I think, for the average person how they'll interpret the guidelines. It's also going to be tough for health departments because now contact tracing is going to be substantially more than what it has already been. Each case will have more contacts because of the change in timing.

AKIKO FUJITA: So what does that mean in terms of what more we know about the virus? Is the chance of infection much higher than we expected? I mean, what specifically does this guideline say about the ability for this virus to spread in a very confined space?

SUZANNE JUDD: That's a great question too. CDC also changed their guidance about two weeks ago on whether or not COVID is airborne. They now say there is the potential that it can become airborne if people are singing or yelling or anything that's going to involve a lot of air and spit coming out basically at the same time. So that means that enclosed spaces like churches and choir concerts, there's the potential for COVID to spread much further beyond the six feet. It can stay in the air longer than just 15 minutes if it's truly airborne. It just changes the way we have to think about managing it.

As for the data, several epidemiologists have questioned why CDC did it. The-- specifically the 15-minute rule comes from one study in a prison, and that's the only one that backs up the data. It's probably out of an abundance of caution that they changed their guidance, but it doesn't appear that COVID is any different than it was back in March.

AKIKO FUJITA: That new guidance, though, it has to be a big concern going into the colder months. And we've heard this from our guests every day who are saying that as the-- you know, as we get to winter people are going to want to stay indoors more. They're going to be-- want to stay in a confined space. You know, when you look at where the numbers are, the case counts are, the positivity rates going up, what's your biggest concern?

We're still in October. We've got a long way to go for the winter. What are you going to be watching?

SUZANNE JUDD: We do. We do. December is typically when influenza peaks, and we think COVID is going to be very similar to influenza. There's a good chance that cases will get so high that we will have to start slowing back down in terms of how much we're interacting with each other. We can't overwhelm the hospitals, so I think that's the big thing everyone's going to be watching. When are the hospitals getting to the point where they're saying, wait a minute, slow-- we have to slow this again.

I think December is going to be a really important pinch point. You've got Thanksgiving, then you've got Christmas, and you've got the other holidays. It's just a time when people are going to be socializing much more than they have been. So there's just that potential for spread that will then lead into January and February when we really see peak hospitalizations for the flu.