What to Know about the Fast-Spreading Delta Variant
A highly contagious form of the coronavirus known as the Delta variant is spreading rapidly and becoming increasingly prevalent around the world. First identified in India in December, Delta has now been identified in 111 countries.
In the United States, the variant now accounts for 83% of sequenced COVID-19 cases, said Rochelle Walensky, director of the Centers for Disease Control and Prevention, at a July 20 Senate hearing. In May, Delta was responsible for just 3% of U.S. cases. The World Health Organization projects that Delta will become the dominant variant globally over the coming months.
So, how worried should you be about the Delta variant? We asked experts some common questions about Delta.
What is a variant?
To understand Delta, it's helpful to first understand what a variant is. When a virus infects a person, it gets into your cells and makes a copy of its genome so it can replicate and spread throughout your body.
In the process of making new copies of itself, the virus can make a mistake in its genetic code. Because viruses are replicating all the time, these mistakes — also called mutations — happen pretty often. A new variant emerges when a virus acquires one or more new mutations and starts spreading within a population.
There are thousands of SARS-CoV-2 variants, but most of them don't substantially change the way the virus behaves. The variants that scientists are most interested in are known as variants of concern. These are versions of the virus with mutations that allow the virus to spread more easily, evade vaccines, or cause more severe disease.
"The vast majority of the mutations that have accumulated in SARS-CoV-2 don't change the biology as far as we're concerned," said Jennifer Surtees, a biochemist at the University of Buffalo who's studying the coronavirus. "But there have been a handful of key mutations and combinations of mutations that have led to what we're now calling variants of concern."
One of those variants of concern is Delta, which is now driving many new COVID-19 infections.
Why is the Delta variant so concerning?
"The reason why the Delta variant is concerning is because it's causing an increase in transmission," said Alba Grifoni, an infectious disease researcher at the La Jolla Institute for Immunology. "The virus is spreading faster and people — particularly those who are not vaccinated yet — are more prone to exposure."
The Delta variant has a few key mutations that make it better at attaching to our cells and evading the neutralizing antibodies in our immune system. These mutations have changed the virus enough to make it more than twice as contagious as the original SARS-CoV-2 virus that emerged in Wuhan and about 50% more contagious than the Alpha variant, previously known as B.1.1.7, or the U.K. variant.
These mutations were previously seen in other variants on their own, but it's their combination that makes Delta so much more infectious.
Do vaccines work against the Delta variant?
The good news is, the COVID-19 vaccines made by AstraZeneca, Johnson & Johnson, Moderna, and Pfizer still work against the Delta variant. They remain more than 90% effective at preventing hospitalizations and death due to Delta. While they're slightly less protective against disease symptoms, they're still very effective at preventing severe illness caused by the Delta variant.
"They're not as good as they were against the prior strains, but they're holding up pretty well," said Eric Topol, a physician and director of the Scripps Translational Research Institute, during a July 19 briefing for journalists.
Because Delta is better at evading our immune systems, it's likely causing more breakthrough infections — COVID-19 cases in people who are vaccinated. However, breakthrough infections were expected before the Delta variant became widespread. No vaccine is 100% effective, so breakthrough infections can happen with other vaccines as well. Experts say the COVID-19 vaccines are still working as expected, even if breakthrough infections occur. The majority of these infections are asymptomatic or cause only mild symptoms.
Should vaccinated people worry about the Delta variant?
Vaccines train our immune systems to protect us against infection. They do this by spurring the production of antibodies, which stick around in our bodies to help fight off a particular pathogen in case we ever come into contact with it.
But even if the new Delta variant slips past our neutralizing antibodies, there's another component of our immune system that can help overtake the virus: T cells. Studies are showing that the COVID-19 vaccines also galvanize T cells, which help limit disease severity in people who have been vaccinated.
"While antibodies block the virus and prevent the virus from infecting cells, T cells are able to attack cells that have already been infected," Grifoni said. In other words, T cells can prevent the infection from spreading to more places in the body. A study published July 1 by Grifoni and her colleagues found that T cells were still able to recognize mutated forms of the virus — further evidence that our current vaccines are effective against Delta.
Can fully vaccinated people spread the Delta variant?
Previously, scientists believed it was unlikely for fully vaccinated individuals with asymptomatic infections to spread Covid-19. But the Delta variant causes the virus to make so many more copies of itself inside the body, and high viral loads have been found in the respiratory tracts of people who are fully vaccinated. This suggests that vaccinated people may be able to spread the Delta variant to some degree.
If you have COVID-19 symptoms, even if you're fully vaccinated, you should get tested and isolate from friends and family because you could spread the virus.
What risk does Delta pose to unvaccinated people?
The Delta variant is behind a surge in cases in communities with low vaccination rates, and unvaccinated Americans currently account for 97% of hospitalizations due to COVID-19, according to Walensky. The best thing you can do right now to prevent yourself from getting sick is to get vaccinated.
Gigi Gronvall, an immunologist and senior scholar at the Johns Hopkins Center for Health Security, said in this week's "Making Sense of Science" podcast that it's especially important to get all required doses of the vaccine in order to have the best protection against the Delta variant. "Even if it's been more than the allotted time that you were told to come back and get the second, there's no time like the present," she said.
With more than 3.6 billion COVID-19 doses administered globally, the vaccines have been shown to be incredibly safe. Serious adverse effects are rare, although scientists continue to monitor for them.
Being vaccinated also helps prevent the emergence of new and potentially more dangerous variants. Viruses need to infect people in order to replicate, and variants emerge because the virus continues to infect more people. More infections create more opportunities for the virus to acquire new mutations.
Surtees and others worry about a scenario in which a new variant emerges that's even more transmissible or resistant to vaccines. "This is our window of opportunity to try to get as many people vaccinated as possible and get people protected so that so that the virus doesn't evolve to be even better at infecting people," she said.
Does Delta cause more severe disease?
While hospitalizations and deaths from COVID-19 are increasing again, it's not yet clear whether Delta causes more severe illness than previous strains.
How can we protect unvaccinated children from the Delta variant?
With children 12 and under not yet eligible for the COVID-19 vaccine, kids are especially vulnerable to the Delta variant. One way to protect unvaccinated children is for parents and other close family members to get vaccinated.
It's also a good idea to keep masks handy when going out in public places. Due to risk Delta poses, the American Academy of Pediatrics issued new guidelines July 19 recommending that all staff and students over age 2 wear face masks in school this fall, even if they have been vaccinated.
Parents should also avoid taking their unvaccinated children to crowded, indoor locations and make sure their kids are practicing good hand-washing hygiene. For children younger than 2, limit visits with friends and family members who are unvaccinated or whose vaccination status is unknown and keep up social distancing practices while in public.
While there's no evidence yet that Delta increases disease severity in children, parents should be mindful that in some rare cases, kids can get a severe form of the disease.
"We're seeing more children getting sick and we're seeing some of them get very sick," Surtees said. "Those children can then pass on the virus to other individuals, including people who are immunocompromised or unvaccinated."
Inside Scoop: How a DARPA Scientist Helped Usher in a Game-Changing Covid Treatment
Amy Jenkins is a program manager for the Defense Advanced Research Projects Agency's Biological Technologies Office, which runs a project called the Pandemic Prevention Platform.
Amy Jenkins was in her office at DARPA, a research and development agency within the Department of Defense, when she first heard about a respiratory illness plaguing the Chinese city of Wuhan. Because she's a program manager for DARPA's Biological Technologies Office, her colleagues started stopping by. "It's really unusual, isn't it?" they would say.
At the time, China had a few dozen cases of what we now call COVID-19. "We should maybe keep an eye on that," she thought.
Early in 2020, still just keeping watch, she was visiting researchers working on DARPA's Pandemic Prevention Platform (P3), a project to develop treatments for "any known or previously unknown infectious threat," within 60 days of its appearance. "We looked at each other and said, 'Should we be doing something?'" she says.
For projects like P3, groups of scientists—often at universities and private companies—compete for DARPA contracts, and program managers like Jenkins oversee the work. Those that won the P3 bid included scientists at AbCellera Biologics, Inc., AstraZeneca, Duke University, and Vanderbilt University.
At the time Jenkins was talking to the P3 performers, though, they didn't have evidence of community transmission. "We would have to cross that bar before we considered doing anything," she says.
The world soon leapt far over that bar. By the time Jenkins and her team decided P3 should be doing something—with their real work beginning in late February--it was too late to prevent this pandemic. But she could help P3 dig into the chemical foundations of COVID-19's malfeasance, and cut off its roots. That work represents, in fact, her roots.
In late February 2020, DARPA received a single blood sample from a recovered COVID-19 patient, in which P3 researchers could go fishing for antibodies. The day it arrived, Jenkins's stomach roiled. "We get one shot," she thought.
Fighting the Smallest Enemies
Jenkins, who's in her early 40s, first got into germs the way many 90s kids did: by reading The Hot Zone, a novel about a hemorrhagic fever gone rogue. It wasn't exactly the disintegrating organs that hooked her. It was the idea that "these very pathogens that we can't even see can make us so sick and bring us to our knees," she says. Reading about scientists facing down deadly disease, she wondered, "How do these things make you so sick?"
She chased that question in college, majoring in both biomolecular science and chemistry, and later became an antibody expert. Antibodies are proteins that hook to a pathogen to block it from attaching to your cells, or tag it for destruction by the rest of the immune system. Soon, she jumped on the "monoclonal antibodies" train—developing synthetic versions of these natural defenses, which doctors can give to people to help them battle an early-stage infection, and even to prevent an infection from taking root after an exposure.
Jenkins likens the antibody treatments to the old aphorism about fishing: Vaccines teach your body how to fish, but antibodies simply give your body the pesca-fare. While that, as the saying goes, won't feed you for a lifetime, it will last a few weeks or months. Monoclonal antibodies thus are a promising preventative option in the immediate short-term when a vaccine hasn't yet been given (or hasn't had time to produce an immune response), as well as an important treatment weapon in the current fight. After former president Donald Trump contracted COVID-19, he received a monoclonal antibody treatment from biotech company Regeneron.
As for Jenkins, she started working as a DARPA Biological Technologies Office contractor soon after completing her postdoc. But it was a suit job, not a labcoat job. And suit jobs, at first, left Jenkins conflicted, worried about being bored. She'd give it a year, she thought. But the year expired, and bored she was not. Around five years later, in June 2019, the agency hired her to manage several of the office's programs. A year into that gig, the world was months into a pandemic.
The Pandemic Pivot
At DARPA, Jenkins inherited five programs, including P3. P3 works by taking blood from recovered people, fishing out their antibodies, identifying the most effective ones, and then figuring out how to manufacture them fast. Back then, P3 existed to help with nebulous, future outbreaks: Pandemic X. Not this pandemic. "I did not have a crystal ball," she says, "but I will say that all of us in the infectious diseases and public-health realm knew that the next pandemic was coming."
Three days after a January 2020 meeting with P3 researchers, COVID-19 appeared in Seattle, then began whipping through communities. The time had come for P3 teams to swivel. "We had done this," she says. "We had practiced this before." But would their methods stand up to something unknown, racing through the global population? "The big anxiety was, 'Wow, this was real,'" says Jenkins.
While facing down that realness, Jenkins was also managing other projects. In one called PREPARE, groups develop "medical countermeasures" that modulate a person's genetic code to boost their bodies' responses to threats. Another project, NOW, envisions shipping-container-sized factories that can make thousands of vaccine doses in days. And then there's Prometheus—which means "forethought" in Greek, and is the name of the god who stole fire and gave it to humans. Wrapping up as COVID ramped up, Prometheus aimed to identify people who are contagious—with whatever—before they start coughing, and even if they never do.
All of DARPA's projects focus on developing early-stage technology, passing it off to other agencies or industry to put it into operation. The orientation toward a specific goal appealed to Jenkins, as a contrast to academia. "You go down a rabbit hole for years at a time sometimes, chasing some concept you found interesting in the lab," she says. That's good for the human pursuit of knowledge, and leads to later applications, but DARPA wants a practical prototype—stat.
"Dual-Use" Technologies
That desire, though, and the fact that DARPA is a defense agency, present philosophical complications. "Bioethics in the national-security context turns all the dials up to 10+," says Jonathan Moreno, a medical ethicist at the University of Pennsylvania.
While developing antibody treatments to stem a pandemic seems straightforwardly good, all biological research—especially that backed by military money—requires evaluating potential knock-on applications, even those that might come from outside the entity that did the developing. As Moreno put it, "Albert Einstein wasn't thinking about blowing up Hiroshima." Particularly sensitive are so-called "dual-use" technologies—those tools that could be used for both benign and nefarious purposes, or are of interest to both the civilian and military worlds.
Moreno takes Prometheus itself as an example of "dual-use" technology. "Think about somebody wearing a suicide vest. Instead of a suicide vest, make them extremely contagious with something. The flu plus Ebola," he says. "Send them someplace, a sensitive environment. We would like to be able to defend against that"—not just tell whether Uncle Fred is bringing asymptomatic COVID home for Christmas. Prometheus, Jenkins says, had safety in mind from the get-go, and required contenders to "develop a risk mitigation plan" and "detail their strategy for appropriate control of information."
To look at a different program, if you can modulate genes to help healing, you probably know something (or know someone else could infer something) about how to hinder healing. Those sorts of risks are why PREPARE researchers got their own "ethical, legal, and social implications" panel, which meets quarterly "to ensure that we are performing all research and publications in a safe and ethical manner," says Jenkins.
DARPA as a whole, Moreno says, is institutionally sensitive to bioethics. The agency has ethics panels, and funded a 2014 National Academies assessment of how to address the "ethical, legal, and societal issues" around technology that has military relevance. "In the cases of biotechnologies where some of that research brushes up against what could legitimately be considered dual-use, that in itself justifies our investment," says Jenkins. "DARPA deliberately focuses on safety and countermeasures against potentially dangerous technologies, and we structure our programs to be transparent, safe, and legal."
Going Fishing
In late February 2020, DARPA received a single blood sample from a recovered COVID-19 patient, in which P3 researchers could go fishing for antibodies. The day it arrived, Jenkins's stomach roiled. "We get one shot," she thought.
As scientists from the P3-funded AbCellera went through the processes they'd practiced, Jenkins managed their work, tracking progress and relaying results. Soon, the team had isolated a suitable protein: bamlanivimab. It attaches to and blocks off the infamous spike proteins on SARS-CoV-2—those sticky suction-cups in illustrations. Partnering with Eli Lilly in a manufacturing agreement, the biotech company brought it to clinical trials in May, just a few months after its work on the deadly pathogen began, after much of the planet became a hot zone.
On November 10—Jenkins's favorite day at the (home) office—the FDA provided Eli Lilly emergency use authorization for bamlanivimab. But she's only mutedly screaming (with joy) inside her heart. "This pandemic isn't 'one morning we're going to wake up and it's all over,'" she says. When it is over, she and her colleagues plan to celebrate their promethean work. "I'm hoping to be able to do it in person," she says. "Until then, I have not taken a breath."
Everyone Should Hear My COVID Vaccine Experience
Dr. Ranney immediately after receiving her first dose of the Pfizer vaccine on December 18, 2020.
On December 18th, 2020, I received my first dose of the Pfizer mRNA vaccine against SARS-CoV-2. On January 9th, 2021, I received my second. I am now a CDC-card-carrying, fully vaccinated person.
The build-up to the first dose was momentous. I was scheduled for the first dose of the morning. Our vaccine clinic was abuzz with excitement and hope, and some media folks were there to capture the moment. A couple of fellow emergency physicians were in the same cohort of recipients as I; we exchanged virtual high-fives and took a picture of socially distanced hugs. It was, after all, the closest thing we'd had to a celebration in months.
I walked in the vaccine administration room with anticipation – it was tough to believe this moment was truly, finally here. I got a little video of my getting the shot, took my obligate vaccine selfie, waited in the observation area for 15 minutes to ensure I didn't have a reaction, and then proudly joined 1000s of fellow healthcare workers across the country in posting #ThisIsMyShot on social media. "Here we go, America!"
The first shot, though, didn't actually do all that much for me. It hurt less than a flu shot (which, by the way, doesn't hurt much). I had virtually no side effects. I also knew that it did not yet protect me. The Pfizer (and Moderna) data show very clearly that although the immune response starts to grow 10-12 days after the first shot, one doesn't reach full protection against COVID-19 until much later.
So when, two days after my first shot, I headed back to work in the emergency department, I kept wondering "Will this be the day that I get sick? Wouldn't that be ironic!" Although I never go without an N95 during patient care, it just takes one slip – scratching one's eyes, eating lunch in a break room that an infected colleague had just been in – to get ill. Ten months into this pandemic, it is so easy to get fatigued, to make a small error just one time.
Indeed, I had a few colleagues fall ill in between their first and second shots; one was hospitalized. This was not surprising, but still sad, given how close they had come to escaping infection.
Scientifically speaking, one doesn't need to feel bad to develop an immune response. Emotionally, though, I welcomed the symptoms as proof positive that I would be protected.
This time period felt a little like we had our learner's permit for driving: we were on our way to being safe, but not quite there yet.
I also watched, with dismay, our failures as a nation at timely distribution of the vaccine. On December 18th, despite the logistical snafus that many of us had started to highlight, it was still somewhat believable that we would at least distribute (if not actually administer) 20 million doses by the New Year. But by December 31, my worst fears about the feds' lack of planning had been realized. Only 14 million doses had gone to states, and fewer than 3 million had been administered. Within the public health and medical community, we began to debate how to handle the shortages and slow vaccination rates: should we change prioritization schemes? Get rid of the second dose, in contradiction to what our FDA had approved?
Let me be clear: I really, really, really wanted my second dose. It is what is supported by the data. After living this long at risk, it felt frankly unfair that I might not get fully protected. I waited with trepidation, afraid that policies would shift before I got it in my arm.
At last, my date for my second shot arrived.
This shot was a little less momentous on the outside. The vaccine clinic was much more crowded, as we were now administering first doses to more people, as well as providing the second dose to many. There were no high fives, no media, and I took no selfies. I finished my observation period without trouble (as did everyone else vaccinated the same day, as is typical for these vaccines). I walked out the door planning to spend a nice afternoon outdoors with my kids.
Within 15 minutes, though, the very common side effects – reported by 80% of people my age after the second dose – began to appear. First I got a headache (like 52% of people my age), then body aches (37%), fatigue (59%), and chills (35%). I felt "foggy", like I was fighting something. Like 45% of trial participants who had received the actual vaccine, I took acetaminophen and ibuprofen to stave off the symptoms. There is some minimal evidence from other vaccines that pre-treatment with these anti-inflammatories may reduce antibodies, but given that half of trial participants took these medications, there's no reason to make yourself suffer if you develop side effects. Forty-eight hours later, just in time for my next shift, the side effects magically cleared. Scientifically speaking, one doesn't need to feel bad to develop an immune response. Emotionally, though, I welcomed the symptoms as proof positive that I would be protected.
My reaction was truly typical. Although the media hype focuses on major negative reactions, they are – statistically speaking – tremendously rare: fewer than 11/million people who received the Pfizer vaccine, and 3/million who received the Moderna vaccine, developed anaphylaxis; of these, all were treated, and all are fine. Compare this with the fact that approximately 1200/million Americans have died of this virus. I'll choose the minor, temporary, utterly treatable side effects any day.
Now, more than 14 days after my second dose, the data says that my chance of getting really sick is, truly, infinitesimally low. I don't have to worry that each shift will put me into the hospital. I feel emotionally lighter, and a little bit like I have a secret super-power.
But I also know that we are not yet home free.
I may have my personal equivalent of Harry Potter's invisibility cloak – but we don't yet know whether it protects those around me, at all. As Dr. Fauci himself has written, while community spread is high, there is still a chance that I could be a carrier of infection to others. So I still wear my N95 at work, I still mask in public, and I still shower as soon as I get home from a shift and put my scrubs right in the washing machine to protect my husband and children. I also won't see my parents indoors until they, too, have been vaccinated.
At the end of the day, these vaccines are both amazing and life-changing, and not. My colleagues are getting sick less often, now that many of us are a week or more out from our second dose. I can do things (albeit still masked) that would simply not have been safe a month ago. These are small miracles, for which I am thankful. But like so many things in life, they would be better if shared with others. Only when my community is mostly vaccinated, will I breathe easy again.
My deepest hope is that we all have – and take - the chance to get our shots, soon. Because although the symbolism and effect of the vaccine is high, the experience itself was … not that big a deal.