With the Delta variant making up more than 98 percent of new sequenced Covid cases in the US, according to the CDC, urgent questions keep arising about whether the Delta variant is more deadly. Here’s what we know so far.
The Delta variant is different from previous forms of the virus in a number of ways. “The virus has taken a sharp turn and has become Delta, which has increased its ferocity,” explains William Schaffner, MD, professor of infectious diseases at Vanderbilt University. “For sure it’s very much more contagious and spreads much more readily from person to person.” In fact, the CDC says the Delta variant is “more than 2x as contagious” as previous forms of the virus. (See how the percentage of cases due to Delta have grown in recent weeks here.)
“At the moment, it’s honing in particularly on unvaccinated people,” he adds. And it’s spreading rapidly—”its contagiousness is so superior to other strains, you can think of it in Olympic terms. It has outrun the other strains and become the dominant one,” Dr. Schaffner says.
Some research suggests that the efficacy of vaccines may be lower against Delta than they were against the forms of the virus circulating when the vaccines were originally tested, although health experts stress that the vaccine, and possibly a booster shot, is still the strongest protection you can get against SARS CoV-2, the coronavirus that causes Covid.
Delta is also able to be spread by people who are vaccinated. The CDC was alerted to this around July 4, when at least three quarters of people among roughly 470 cases that were clustered around Provincetown, MA there were vaccinated. (Hence the agency’s updated recommendations about mask wearing for vaccinated people that caused a stir in July.) There’s some evidence that vaccinated people shed the virus for a shorter period of time.
How else is the Delta variant different?
The Delta variant also seems to be affecting younger people in greater numbers than other variants did. In the week ending August 21, people ages 18 to 49 made up the largest group of people hospitalized with Covid, according to preliminary data from the CDC.
A New York Times story on August 3 reported doctors as saying they are seeing more hospitalizations in unvaccinated people in their 20s and 30s. They also say that this age group’s condition seems to deteriorate faster than the people in that age range that they saw last year. “Doctors have coined a new phrase to describe them: ‘younger, sicker, quicker,’” the story states.
Is Delta more deadly?
“The question is whether once you are infected, are you more likely to have serious disease with this Delta strain? And the answer is maybe,” says Dr. Schaffner. “We don’t have definitive studies on that yet.”
What we do know so far, however, is that people who are unvaccinated are not only more likely to get Covid, they’re more likely to be hospitalized from it—in May through July, nearly 98 percent of people hospitalized with the disease in the US were unvaccinated, according to the Peterson-KFF Health System Tracker. Vaccinated people who get Covid are likelier to have milder forms of the disease, the CDC says.
And Delta is likelier than other forms to land you in the hospital—people infected with Delta variant are twice as likely to be hospitalized as those infected with the Alpha variant, according to a new study from The Lancet Infectious Diseases.
So if you are hospitalized with an infection caused by the Delta variant, is your case and outcome worse than if you’d been infected with another variant? That gets back to what Dr. Schaffner was saying. It’s not totally clear yet, but the CDC says that “some data suggest the Delta variant might cause more severe illness than previous variants in unvaccinated people.”
Delta or no Delta, “the first thing I would say is ‘let’s worry about Covid,” Dr. Schaffner says. That means doing everything you can to protect yourself from infection from any strain.
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