What’s the Real Deal With the Delta Variant?

Get all the details on the latest COVID-19 mutation.

by Erin L. Boyle Health Writer

We’ve been hearing more and more about COVID-19’s latest contribution to the country’s collective stress level: The Delta variant. You likely have questions. Like… what is this mutation, why does it matter, and how will it impact my daily life?

It’s still early days with Delta, so there are things we don’t know. The things we do know? Delta was first reported in December 2020 and has since spread rapidly around the world. As of mid-July, it’s now the dominant strain in the U.S., representing 83% of new cases of COVID (up from just 10% of cases in the U.S. a month ago!). In mid-July 2021, COVID cases were up by nearly 70% in just one week. National Institute of Allergy and Infectious Diseases Director Anthony Fauci, M.D., has called the variant “the greatest threat” to eliminating COVID-19 in the U.S., mainly in the unvaccinated population.

Does the COVID Vaccine Protect Against the Delta Variant?

Now for the good news: Vaccinations seem to be holding strong against this strain—the Pfizer-BioNTech vaccine has been 96% effective against hospitalization with Delta according to U.K. data, and the Moderna and Johnson & Johnson vaccines are showing only slightly reduced efficacy. Still, there have been reports of “breakthrough” cases in fully vaccinated people who have caught this strain of COVID. In Israel, up to half of new infections from the Delta variant are in people either vaccinated or recovered from COVID, according to news reports, and around 90% of newly infected people over the age of 50 were fully vaccinated.

Concern over the Delta variant has officials in public health circles debating the merits of another mask mandate. So far, the Centers for Disease Control and Prevention (CDC) continues to advise fully vaxxed Americans who aren’t sick that they don’t need to wear a mask except where businesses/local/state require (unvaccinated people should still wear one), but after a welcome return to normalcy for the first half of the summer, it’s becoming clear we’re not quite out of the woods yet.

What the Experts Say

Where are we, exactly? For a little perspective, we talked with public health expert Jeni Stolow, Ph.D., an assistant professor of instruction in social and behavioral sciences at Temple University in Philadelphia and part of the World Health Organization’s Global Outbreak Alert & Response Network (GOARN) Research Focal Point for Risk Communication and Community Engagement for COVID-19.

HealthCentral: How worried should we be about the Delta strain if we’re fully vaxxed—and if there isn’t reason to worry, then why are we hearing so much about it?

Jeni Stolow, Ph.D.: First, I don’t want people to worry, I want people to be informed. I think the reason why you’re hearing so much about it, is, it’s going to be a problem with people who are not vaccinated, and it’s going to be a problem and spread in areas that have low vaccination rates. Right now, we’re seeing 95% to 99% of COVID hospitalizations in the U.S. are among unvaccinated people. For me, that’s the best evidence of why you should get vaccinated and what it means if you don’t.

HC: Where did this strain come from and how serious is it?

Stolow: It was a variant that started in India. The WHO and the scientific community are using Greek alphabet letters to not stigmatize these different strains and countries and people where these are popping up. I want to stress that variants are expected. It happens with every virus, because this is what viruses do. Every time they reproduce, there’s the opportunity to mutate. Their life goal is just to copy and copy as fast and efficiently as possible.

But the virus doesn’t want to be super-severe. It doesn’t want to kill its host, because then it wouldn’t be able to spread. I always tell my students, a virus wants to be stickier, but less sick-ier every year. It wants to make sure it will spread really, really well, which is what we see in Delta. It’s more contagious, meaning it’s easier to transmit.

HC: Why did the Delta variant take off the way it did?

Stolow: When you have viruses that are reproducing and spreading all around the world, this will happen. Some people are vaccinated, some people aren’t. People are traveling when maybe they shouldn’t be or are not adhering to protocols—and this is what’s going to happen. Don’t get me wrong, there are inequities and inequalities, injustices, and unsustainable practices at play that are causing true barriers for people to get vaccinated here in the U.S. as well as globally. But it is so important to get vaccinated as soon as possible [if you can] because the more people who are vaccinated, the less opportunity the virus has to reproduce and mutate, so the fewer strains we’re going to see.

HC: Why haven’t other strains caught on in the same way?

Stolow: Dumb luck. It’s all about what mutation happens and if it works for the virus. But the more it’s able to reproduce, the more opportunity it has for an advantageous mutation. The flu is a perfect example. Every year, we have different strains of the flu. And we hear about that all the time but we don’t think about it. Because of our actions with COVID protection, we might actually have a way better [potential] flu season coming up. The flu was unable to reproduce and spread as much as it has in past years and there are fewer strains, meaning it could potentially be a less severe flu season. That’s great evidence that prevention for one respiratory virus can be beneficial for the mitigation of others.

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HC: How is the Delta variant different than the original COVID virus first reported in Wuhan, China?

Stolow: It’s definitely that whole idea of it being stickier or easier to transmit. So it’s faster to transmit and better at transmitting. So far, that’s all we really know about it. I don’t want to say conclusively that it’s more severe—I think symptoms are really up in the air with COVID. Think about people you know who’ve had COVID: They’ve all had different symptoms, the severity of symptoms is different, the types of symptoms are different. I’m not comfortable saying that if you have Delta, you’re going to get “these symptoms,” because it’s so dependent on the person, the viral load, and a variety of other factors.

HC: Is there anything people should be doing differently to protect themselves against the Delta variant?

Stolow: I recognize that there are different recommendations popping up left and right. And there are medical, political, and economic reasons for that. It’s so hard. Here in the U.S., we have 50 different countries [essentially]. I do not envy anyone at the CDC right now. But I will say, why not be on the safe side, right? So for example, I’m telling my family and my friends, if you’re not vaccinated, if you cannot be vaccinated, if you have children who are under the age limit to be vaccinated, wear a mask. It’s not going to do you harm, so why not? Delta is becoming the most dominant strain here in the U.S., and especially in certain areas of the U.S., so keep masking. I’m fully vaccinated and I’m still masking in certain situations because it is peace of mind. Why not be safe instead of sorry?

HC: What are those situations where you’re still masking?

Stolow: I feel like it’s a, if-then-what [situation]. So if it is two people who are both vaccinated, for example, my friend and I were both vaccinated, then there’s no problem to go to her house without a mask. If I was in a crowd, for example, Trader Joe’s on a Sunday, then I’m going to wear a mask because I don’t know who is or is not vaccinated, and even if people are vaccinated, I can’t physically distance. If I’m around an older individual or younger individual, so those vulnerable populations, then I’m going to wear a mask. If I’m in a healthcare setting, then I’m going to wear a mask. If I’m using public transportation, I’m going to wear a mask. If I have friends who have traveled, then I ask that they wear a mask around me and me around them for the first week or two just to be safe or until they get tested. If I’m outside, or at a park, I’m not going to wear a mask. I’m definitely more cautious than I’m sure other people are being… I think it comes from what I do, but also, why not be cautious?

HC: So what’s the take-away with Delta?

Stolow: Please get vaccinated. The sooner everyone gets vaccinated, the quicker we can get back to quote-unquote normal. Until then, we’re just going to keep seeing these strains and we’re going to keep having problems. It’s not even the only one: There are several strains that are circulating—Delta is just one that’s the hot topic. So wear a mask, especially if you don’t know who you’re around [or if they’re unvaccinated], and wash your hands.

Erin L. Boyle
Meet Our Writer
Erin L. Boyle

Erin L. Boyle, the senior editor at HealthCentral from 2016-2018, is an award-winning freelance medical writer and editor with more than 15 years’ experience. She’s traveled the world for a decade to bring the latest in medical research to doctors. Health writing is also personal for her: she has several autoimmune diseases and migraines with aura, which she writes about for HealthCentral. Learn more about her at erinlynnboyle.com. Follow her on Twitter @ErinLBoyle.