Doctor explains why COVID-19 variants are more contagious

Some preliminary studies are shedding light on the new coronavirus variants spreading around the globe. Dr. Susannah Hills, a pediatric airway surgeon and assistant professor of ENT at New York Presbyterian/Columbia University, joins CBSN to explain what we know about several of the major variants, plus the idea that people who've recovered from COVID-19 may only need one dose of vaccine.

Video Transcript

ANNE-MARIE GREEN: And we want to turn back to the coronavirus pandemic now and the devastating toll that it is taking on our nation. More than a half million Americans have fallen victim to the disease across the globe. Nearly 2.5 million people have died. So for more on this, let's bring in Dr. Susannah Hills. She's a pediatric airway surgeon and assistant professor of ENT at New York Presbyterian Columbia University.

Thank you so much for joining us. So doctor, we're learning more about these new variants that are spreading across the globe, just how potent they are, just how challenging they may be. Give us an idea, give us a snapshot of what we have learned so far about them.

SUSANNAH HILLS: Well, we've certainly seen in looking at the UK variant that it has an increased ability to be transmitted or to spread from person to person. And we've already seen here in the United States that the rate of this UK variant or the number of cases is doubling about every 10 days here. We now have 44 states, almost every state in the United States has a case reported.

My guess is probably just about every state, all 50 probably have a case of this UK variant at this point. And there are about 1,500 cases so far. The variant from South Africa that is also showing up here in the US is concerning in a different way. It's also very transmissible, but it has this capacity as well to evade the vaccine-induced immunity that we're trying to get everybody to have with our Pfizer and Moderna vaccines.

And so that's a really concerning finding. And we just had here in New York our first case of a patient with this variant that came from here from New York state. And so far, 10 states in the United States have cases of the South African variant. And there are 22 cases overall. So I think we're going to see these variant strains, particularly the variant from the UK, becoming dominant in the next month or so.

VLADIMIR DUTHIERS: So doctor, new preliminary research suggests that some people who have had the virus may only need one dose of the vaccine. We should note that this has not yet been peer reviewed or published in a scientific journal. It was first reported in "The Wall Street Journal." But it does come after similar findings highlight the immune benefits after the first injection. Break this down for us.

SUSANNAH HILLS: Yeah, Vlad, there is a lot to unpack there. But here's how I think about vaccine-induced immunity. On the one hand, you've got the level of immunity that you get from a vaccine. So when you think about the Moderna and Pfizer vaccines, two doses gives you, like, 95% protection. It gives a really high level of protection.

When you look at giving people one dose, you know, there was recent data that's been looked at that's come out of Israel, you look at people who have gotten one dose, the suggestion is, right, that after a dose, when you look at patients about 15 to 28 days later, they've got maybe 85% protection. That sounds really good. But you also have to consider, on the other hand, the durability of that vaccine response.

For how long does that protection last? And we just have no idea with that single dose. But we certainly can assume that it's going to be less than with two doses. When we look at patients who've gotten two doses of vaccine, we know from data that just came out in the "New England Journal of Medicine" last month, the vaccine trials continue to follow patients long term.

At least three to four months out from getting that second dose, patients are having a really strong level of protection. And the manufacturers think it's likely to last at least a year. So you get a significantly longer level of protection with two doses. There's also this third variable to consider now, which is these variant strains. And when you get two doses of vaccine, you get a broader array of antibodies.

So you have better protection potentially against some of these variant strings. And we know already the variants are becoming more prevalent in the United States. We know particularly with that variant from South Africa that it has a capacity to evade the vaccine response already.

And so the concern is as these variant strains start spreading more and more, if we have people who have single doses, they may be more susceptible also to these variant strains. And that's going to be a big concern in the coming months. So two doses gives you a stronger level of protection, a longer lasting protection, and potentially more protection against these variant strains.

ANNE-MARIE GREEN: So the CDC recently revised its school reopening guidance according to the severity of the outbreak in their locations. But then it also-- it was also sort of newly stated that students could go back to the classroom without teachers getting inoculated first. But then yesterday, and I ask people to follow along, yesterday, the agency released a report that suggested its educator to educator transmission, followed by educator to student transmission, resulted in a faster spread of the disease.

I hope people understood what I said. But the overall question, though, for you is, what's your take? In your medical opinion, is it safe to open schools? Should teachers perhaps be pushed closer to the front of the line when it comes to inoculation?

SUSANNAH HILLS: Yeah. Here's what I want people to remember about this new data that you just mentioned, Anne-Marie. They looked at these schools in Georgia. They found about nine clusters of COVID cases from December and January of 2020 and 2021. And when they looked closely at the protective measures that were in place, they found that there were significant deficiencies in mask wearing and the social distancing was not maintained.

Many students were less than three feet apart. So that's what we want to remember here about this information. And it speaks to the fact that these protective measures are so important when we're reopening schools. I still believe that opening school is safe if the protective measures are in place.

We had data from last fall from Wisconsin, for example, and North Carolina and these other school systems had incredibly low rates of transmission because they did such a great job, particularly with masking, but with all of these measures that the CDC is recommending. So I think this is an example of why these measures are so important and what happens maybe when there are some gaps.

And I think also, as you mentioned in your lead there, we saw cases of teacher to student transmission. And so I think this conversation about it not being able to be passed between children and adults, for example, we need to really kind of start thinking about it an illness that is passed from children to adults. And we're going to see more and more cases of children being infected with this virus as well.

We've already had 3 million positive cases in children of this virus. As far as teachers go, I think the vaccination is incredibly important. I think they should be prioritized. We have 28 states and DC that are already prioritizing vaccines for teachers. And I think all 50 states should be doing that because, yeah, nobody should have to work in a place where they don't feel safe.

VLADIMIR DUTHIERS: All right. Dr. Hills, thank you so much, as always, we appreciate it.

SUSANNAH HILLS: Thanks, guys.