There are multiple coronavirus variants circulating around the globe since COVID-19 first emerged as a threat some 18 months ago. The latest one to create concern is the delta variant, first detected December 2020 in India. Considered around 60 percent more transmissible than the already highly infectious alpha variant first detected in the U.K., delta has spread to at least 80 countries, including the United States, and is now the U.K.'s most dominant strain, responsible for 91 percent of new cases.
Designated by the World Health Organization (WHO) as a global "variant of concern" (VOC), delta is being blamed for the second deadly wave of infections that have decimated India, a country that on June 9, reached a world record daily high of more than 6,000 deaths in one day.
"It potentially could be one of the more difficult viruses to date," says Dr. Paul Goepfert, a professor of medicine at the University of Alabama at Birmingham and an expert in vaccine design. "We'll just have to see if it's more problematic."
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What Is the Delta Variant?
Coronavirus disease, or COVID-19, is caused by a single species of virus known as SARS-CoV-2. When the original virus, also called "normal," or "wild type," replicates, or copies itself, the sequence of its molecules, called nucleotides, sometimes changes from the original virus. These changes are called mutations. Most of the time, these variations don't work or make the virus weaker.
But sometimes they can make the virus stronger, more contagious or more resistant to the immune system. These variations of the wild-type virus — or variants — catch the eye of health officials in the global SARS-CoV-2 laboratory network at the WHO's Virus Evolution Working Group. The group is tasked with quickly detecting variants and assessing their possible impact.
Delta is the fourth global variant of concern WHO has identified since the pandemic began. The three others — alpha, beta and gamma — were first identified in the United Kingdom, South Africa and Brazil, respectively. Scientifically, the delta variant is known as B.1.617.2.
The delta variant has become a VOC due to some mutations in the spike protein, says Mehul Suthar, assistant professor of pediatrics at Emory Vaccine Center and Yerkes National Primate Research Center.
At least four mutations in the delta variant have been associated with faster spread and/or higher infectivity based on previous variants with similar mutations.
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What Are the Symptoms of the Delta Variant?
With the wild coronavirus, you can expect to have symptoms including fever or chills, cough, shortness of breath or difficulty breathing, fatigue, muscle or body aches, loss of taste or smell, nausea or vomiting, or diarrhea.
However, the delta variant appears to be slightly different. Data gathered from the UK's ZOE COVID Symptom Study app showed people in the U.K. described headaches, sore throats, runny noses and fever to be the No. 1 symptoms.
Blood clots also are a concerning complication of COVID-19. But Dr. Ganesh Manudhane, a cardiologist in Mumbai, India, told Bloomberg he has seen a surprising number and type of blood clots in recent COVID-19 patients across age groups with no past history of abnormal clotting. Several patients developed micro thrombi, or small blood clots, so severe that some developed gangrene and required amputations of fingers or a foot. "We suspect it could be because of the new virus variant," he told Bloomberg.
However, it is important to note that these observations are anecdotal and not based on scientific research at this time.
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How Widespread Is Delta in the U.S.?
The mRNA vaccines are proving their worth in countries where shots are more readily available. Ironically, India is home to the world's largest vaccine manufacturer, but is struggling with a major internal shortage of shots. A little more than 10 percent of the country's population has received one vaccine and, as a result, the country has seen a steady decline in cases since it was engulfed in a deadly second wave this spring.
In the U.S. just over half (53.03 percent) of the U.S. population is fully vaccinated, and both new cases of COVID-19 and related deaths have been trending downward.
But in a White House COVID-19 Response Team press briefing June 22, Fauci Dr. Anthony Fauci, chief medical adviser to the president, said cases of the delta variant have doubled in about two weeks. In early May, the delta variant accounted for just 1.2 percent of cases, he said. Now it accounts for 20.6 percent. He said the U.S. seems to be "following the same pattern" as the U.K., where the delta variant became dominant very quickly and now makes up 99 percent of cases there.
The dominant strain in the U.S. currently is the alpha variant, known by the scientific name B.1.1.7. But Fauci warned that delta could soon become the dominant strain in the U.S. as well. "The delta variant is currently the greatest threat in the U.S. to our attempt to eliminate COVID-19," he said in the press briefing June 22.
And one age group where cases are climbing the most is among the 12- to 20-year-olds. One reason may be because this age group is among the last to get vaccinated, Goepfert says.
"Initially we try to vaccinate our older population and rightfully so and we're seeing the benefits of that in decreased hospitalizations," Goepfert says. "But now we're seeing [infections] that are mainly in younger people and we're focusing on the fact it's not a completely benign infection in younger people. They're not as at-risk but they have problems too with this and some of them get really, really sick."
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Do COVID Vaccines Protect Against the Delta Variant?
It's too early to say for sure whether approved COVID-19 vaccines protect against the delta variant, Goepfert says, but early data is promising.
According to a preprint study conducted in the U.K., one dose of the two-dose Pfizer vaccine provided about 33 percent protection against the delta variant. Two doses were 88 percent effective.
No data has been published, to date, on the efficacy of the two other vaccines approved by the Food and Drug Administration (FDA) for emergency use in the U.S. — the two-shot Moderna vaccine or the one-shot Johnson & Johnson vaccine — against the delta variant. But Fauci said in the June 22 press briefing he believes in the vaccines' efficacy.
"The effectiveness of the vaccines — in this case, two weeks after the second dose of Pfizer-BioNTech — was 88 percent effective against the delta and 93 percent effective against the alpha when you're dealing with symptomatic disease," Fauci said. "We have the tools, so let's use them and crush the outbreak."
However, the CDC notes the delta variant might be able to avoid the antibodies our bodies produce after a vaccination or coronavirus infection. And for those who do get infected, the monoclonal antibody treatments (or treatments for those who have COVID-19) might be less effective against the delta variant. And that's not good because a study published June 14 in the science journal the Lancet found that those infected by the delta variant were about twice as likely to be hospitalized than those infected by the alpha variant.
Both Moderna and Pfizer's COVID vaccines are made using mRNA technology. Previous studies have shown that a full double-dose of Pfizer's or Moderna's vaccine provides 95 percent and 94 percent protection against the original virus, respectively. Johnson & Johnson's one-shot vaccine, which uses a modified adenovirus, was found 72 percent effective against the wild-type virus.
"We really got lucky especially with the mRNA vaccines that we achieved such a high protective efficacy. This is something that was not expected when these vaccines were first generated," Suthar says. "I think 50 percent is great but when you start hitting 90 percent, that's even better."
"These vaccines are remarkable," Goepfert agrees. "Even in older adults, it works really, really well which is unusual for most any vaccine that we have. So that's just remarkable."
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Originally Published: Jun 14, 2021
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