Three Guidelines To Understanding The Delta Variant : Short Wave Delta is quickly becoming the dominant coronavirus variant in multiple countries. The variant has spread so fast because it is more contagious than the variants that came before it. At the same time, the U.S. is equipped with highly effective vaccines. Ed Yong, science writer for The Atlantic, talks with Maddie about the interaction between the variants and the vaccines and how that will be crucial in the months ahead.

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Three Guidelines To Understanding The Delta Variant

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MADDIE SOFIA, HOST:

You're listening to SHORT WAVE...

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SOFIA: ...From NPR.

Hey, everybody. Maddie Sofia here. And today, we're joined by an old friend of the show, Atlantic science writer Ed Yong.

So, Ed, anything - any big personal accomplishments since we've had you on the show or...

ED YONG: I got a dog.

SOFIA: He also got a Pulitzer Prize for his coverage of the coronavirus pandemic. His most recent coronavirus reporting is about the delta variant...

YONG: Delta was first identified in India. It's been incredibly well characterized.

SOFIA: ...A strain of the coronavirus that has rapidly spread throughout many countries, including the U.S.

YONG: Where it is already picking up a lot of steam.

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MEG TIRRELL: Delta is the predominant variant here in the United States.

UNIDENTIFIED REPORTER: As the delta variant spreads primarily through areas with low vaccination rates, half the states now reporting an increase in new cases.

TIRRELL: Hospital admissions also starting to tick higher, now up 7% to 2,000 a day here in the U.S.

SOFIA: The delta variant has spread so fast because it is much more contagious than any of the other strains we've been up against so far.

YONG: The alpha variant, which people were very worried about earlier on in this year, was already far more transmissible than the original vanilla SARS-CoV-2 virus. Delta is even more transmissible than that by anywhere from 35% to 60%, depending on the study that you're looking at.

SOFIA: So we're facing the most contagious variants yet. And at the same time, in the U.S., we're equipped with highly effective vaccines. And that interaction between the vaccines and the variants will be crucial in the months ahead.

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SOFIA: So today on the show, Ed's going to walk us through three principles that help us understand that interaction and serve to guide us through our near-term future. I'm Maddie Sofia, and this SHORT WAVE, the daily science podcast from NPR.

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SOFIA: OK, Ed. So your piece is broken down into three major points - first, how the vaccines are holding up against variants like the delta variant; second, how unvaccinated populations are being impacted by this variant; and then third, the longer unvaccinated or vulnerable populations are under siege, the less likely our vaccines will continue to beat them. So let's start by talking about vaccines. So far, the vaccines have worked against all the variants we've faced before. Has that changed with the delta variant?

YONG: I think it's still good news. It doesn't look as if delta has really made too much of a dent into the effectiveness of the vaccines, which are still very much living up to the promise, the extraordinary promise that they showed in the clinical trials from last year.

So, for example, we have data from the U.K. showing that two doses of the Pfizer vaccine are still 88% effective at preventing symptomatic delta infections and 96% effective at preventing hospitalizations. So that 88% number - that's a little less than the, you know, 90-plus percent that we saw in previous studies against the original virus, but that's still pretty good, right?

SOFIA: Right.

YONG: Like, if we had an announcement at the end of last year saying new vaccines are coming out; they're going to be 88% effective against the virus, everyone would've been ecstatic.

SOFIA: Right.

YONG: So we should still be ecstatic, right? Vaccination is still a truly extraordinary defense that we've been given against the pandemic, delta included.

SOFIA: Yeah, absolutely. And you made a really good point in there, and that's with Pfizer and the Moderna vaccines, those are two-vaccine shots, both shots, because it is a - it's a much grimmer picture with only a single dose of those vaccines.

YONG: That's right. So full vaccination, with a huge emphasis on full, is really important. So that same set of data from the U.K. suggested that a single dose of Pfizer's vaccine is only 33% effective at preventing symptomatic infection. Now, obviously, 33% is better than 0%.

SOFIA: Right.

YONG: But it's still not great. That matters for the roughly 1 in 10 people in the U.S. who've had their first shot but have missed their second shot appointments.

SOFIA: Yeah, yeah. And as expected, there have been some breakthrough cases of COVID in fully vaccinated people, right?

YONG: Yeah.

SOFIA: That's expected. How should we think about those in the world of the delta variant and just in general?

YONG: So 88% is not 100%. Know that none of the vaccines are completely protective. That being said, people who do get these so-called breakthrough infections do seem to have a much better time of it than if they had not been vaccinated at all. So the infections tend to be milder. They tend to be shorter. The viral load tends to be lower, which means that you are much less likely to get extremely sick if you have been vaccinated and, you know, and obviously much less likely to die.

SOFIA: Yeah, yeah. You know, with transmission rates being so high for this variant, with there being some totally anticipated breakthrough infections with community spread increasing in unvaccinated populations, I mean, do you anticipate this leading to any changes in mask guidelines coming out of the CDC or anything like that?

YONG: I think it should do. Whether it actually does or not is another question. The critical issue here, which I think not enough people are talking about, is the transmission of the virus from people who've already been vaccinated. We don't really know enough about those dynamics. We know from past studies that certainly against the original virus, the vaccines do a good job of stopping vaccinated people from spreading the virus should they become infected. But there are a few worrying signs, I think, that this is less true for delta, that the vaccines are less good at stopping infected people from spreading the delta variant on to others. And I think that raises the worrying risk scenario where you might be fine if you're vaccinated, you might get delta and experience no symptoms or very mild symptoms, but you might still be able to slingshot that virus on to other people around you, especially those who've been unvaccinated.

SOFIA: Right, right.

YONG: And that, I think, is a strong reason to continue use investing in other protective measures, and especially masks. Like, I still wear masks indoors.

SOFIA: Yeah, yeah. OK, so that's the main focus. That's principle one of your piece about vaccines and vaccinations. Let's talk about what's going on with unvaccinated people.

YONG: Bad news. Unvaccinated people are in many ways more danger than ever because of the variants. To some extent, they'll get protection from the immunity of vaccinated people around them. But, you know, the reality remains that they are now facing more dangerous versions of the same virus that had already been causing problems for unvaccinated people, i.e., all of us, last year. And that, I think, is tremendously worrying.

You know, the U.S. has only fully vaccinated, I believe, just over half of the population. There are going to be groups, like immunocompromised people, for whom the vaccines won't work as well. There are people who still haven't been able to get access to the vaccines. There are young children, of course, who are not eligible for vaccination yet.

SOFIA: Right.

YONG: And I think we will see as the year progresses, and especially as other protective measures are lifted, we will see the delta variant and other variants tear through unvaccinated communities. And, you know, crucial thing to remember about unvaccinated communities is that they are communities, right? People who aren't vaccinated tend to cluster socially and geographically, which creates these pockets of vulnerability that allow variants like delta to spread more easily. And, you know, of course, those pockets of vulnerability map onto existing pockets of social vulnerability, people who, for reasons of race or class, have had a harder time getting access to vaccinations and still remain vulnerable.

SOFIA: Yeah, yeah. I kind of want to follow up with one group that you mentioned there, immunocompromised folks. Now, that group is obviously a very diverse group of people. But for some, either they can't get vaccinated, or they can but it's hard to know exactly how well the vaccine works for them. And, you know, you write about this a bit, but I haven't seen that much focused on immunocompromised folks. How should they be thinking about the delta variant, and what do you think we should be doing to protect those vulnerable groups?

YONG: Yeah, I think it's still a very worrying situation for them. I think it must be very difficult seeing so much of the country act as if the pandemic is over when, in fact, it's very much not. It's still going to take a toll on communities that haven't had the opportunity or the privilege to benefit from the shield of vaccination, which is why I think we can't just put all of our eggs into the vaccination basket. Like, we have to still use a lot of the other measures that have worked very well - well, or theoretically could work very well if we actually use them - for controlling the pandemic, full stop. You know, we've already talked about masking, using the outdoors as much as possible, you know, using testing and tracing and all of the other stuff that we spent a year and a half talking about, especially at a time when vaccination rates are plateauing in this country.

SOFIA: Right.

YONG: It's really important to think about the vaccines as part of a suite of measures that we use to bring the pandemic under control.

SOFIA: Absolutely. Absolutely. OK, so the last point that you touch on in your piece is that the longer variants, like the delta variant, continue to ravage vulnerable populations, the less likely our vaccines are to hold up against new variants. Walk me through that a little bit.

YONG: Right. So as I said, the vaccines are still holding their own against the variants. A lot of scientists and public health people are worried about the prospect of immune escape. So that's the idea that some variant will emerge that will finally truly break through the protection that the vaccines offer. So it will have mutated in such a way that the immune response that the vaccine triggers no longer blocks it from severely infecting people. I don't think this is just a theoretical risk. I think it is a very real one. As we said, we've already seen delta slightly erode the protection that a single shot of a vaccine provides. You know, it's a worrying indicator of what might happen over the next year or so.

We know that the virus is going to continue evolving, and we know that the more hosts it manages to infect, the more chances it has to evolve into new forms, including some that might finally escape from the immune protection of the vaccines. It's just a probability game now. The more we let the pandemic rage on in unvaccinated communities within the U.S. and in massively unvaccinated countries around the world, the more chances we will get of allowing the evolution of another variant that finally breaks that first principle down.

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SOFIA: All right, Ed. Well, I just want to thank you. With me leaving SHORT WAVE, this will probably be the last time you and I, at least, talk on the show. So I just want to say thank you for tirelessly working to help us and others make sense of this pandemic. I know a little bit about what that costs, so I just want to say thank you so much. It's been an honor to interview you on this show. And congrats on the Pulitzer. You deserve it.

YONG: It's been an honor, too, Maddie. You've been fantastic. And what a service you've done for your listeners in all this time.

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SOFIA: This episode was produced by Rebecca Ramirez, edited by Gisele Grayson and fact-checked by Indi Khera. I'm your host, Maddie Sofia. Thanks so much for listening to SHORT WAVE, the daily science podcast from NPR.

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