Why the delta variant is causing an explosion of cases among the unvaccinated

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Just as millions of people in the United States are feeling that life has returned to normal, the coronavirus’ delta variant emerged as the nation’s most prevalent this week, once again raising the stakes in the struggle to put down the pandemic.

New data from the Centers for Disease Control and Prevention shows that more than half of all new COVID-19 cases in the U.S. were traced to the delta variant, which is believed to be passed more easily to others than any that has come before it. About a third of Americans are fully unvaccinated and, President Joe Biden said during a press conference Tuesday, vulnerable to the delta variant.

“Our fight against this virus is not over,” Biden said.

In counties where COVID rates are currently the highest, there is a direct correlation to the fact that the vast majority of residents are unvaccinated. More than 99 percent of the people who died from COVID-related causes in June were unvaccinated, Dr. Anthony Fauci said on Sunday, and the rise of delta means “we are seeing increased hospitalizations and deaths among unvaccinated individuals,” CDC director Dr. Rochelle Walensky said Thursday.

Here’s what we know about the delta variant and why health experts say it’s more important than ever to get vaccinated.

What’s different about delta

Since it was first identified in October 2020, the delta variant has distinguished itself as the most transmissible known variant of the coronavirus. Without widespread vaccination and rigid adherence to public health measures, such as masking and social distancing, SARS-CoV-2 has been allowed to mutate and evolve over time and will continue to do so.

Data suggest this variant is three times as infectious as the original coronavirus strain, according to Dr. Tom Frieden, former CDC director who founded Resolve to Save Lives. But it remains unclear if this virus is deadlier or leads to more severe illness, said Dr. Yvonne Maldonado, chief of the Division of Pediatric Infectious Diseases at Stanford University School of Medicine. Some data suggest that symptoms associated with a delta variant infection — a runny nose and sore throat — may be slightly different than earlier in the pandemic. For example, the loss of one’s sense of smell is being reported less frequently.

delta-variant-growth

Chart by Megan McGrew/PBS NewsHour

The variant devastated India this spring, smashing global records for daily rates of new infection and threatening to collapse parts of that nation’s health care system. Since then, the World Health Organization has said this variant is on track to dominate all known infections. And, Frieden added, it has moved the goal posts for target vaccination rates.

“The threshold for herd immunity is higher with delta than it was before,” Frieden said.

Globally, those efforts are “failing” to vaccinate people against the virus and remain “billions short” of what is needed to contain the virus’ spread and prevent more mutations and variants, Frieden said. The WHO has projected the goal of getting 70 percent of the world’s population vaccinated against COVID-19 by next year, but Frieden said current rates are “unacceptable” and that millions of people will suffer if more aggressive steps are not taken to ramp up vaccination campaigns.

Some estimates suggest that roughly 10 percent of the world’s population is currently immunized. In most countries, health care workers and at-risk populations are still exposed to potential infection, hospitalization and death due to the virus. A scenario health experts fear is that eventually, if transmission continues unfettered in many parts of the world, another variant could emerge that evades the highly effective vaccines we currently have.

To meet demand, Frieden said companies must share their intellectual property and technical know-how more broadly so that more countries around the globe can have access to vaccines, prevent deaths and reduce the virus’ spread.

“We need to move much faster than what we’re doing,” he said.

Risk for the unvaccinated

Vaccine supply is not the problem in the U.S. Here, 67 percent of U.S. adults are at least partially vaccinated, falling just short of the Biden administration’s goal of having 70 percent of people age 18 or older at least partially vaccinated by the Fourth of July — a benchmark based on earlier estimates of when the U.S. might reach herd immunity. As ofApril 19, the U.S. expanded access to vaccines to virtually all adults, later allowing people as young as 12 to get vaccinated. Yet some states with low vaccination rates have returned unused doses to the federal government — an acknowledgment of the uphill climb public health officials still face in convincing millions of Americans that the coronavirus poses more than a casual threat.

People are forgoing vaccination at their peril, Frieden said.

Across the U.S.,173 counties have reported high rates of COVID-19 infection of more than 100 cases per 100,000 people, Walensky noted during the White House COVID-19 Task Force briefing Thursday. In 93 percent of those counties, public health officials say vaccination rates are extremely low — 40 percent or less.

“This is a very, very dangerous moment to be unvaccinated with this variant circulating,” said Dr. Ashish Jha, dean of the Brown School of Public Health.

Hospital staff are running out of ventilators and respiratory therapists in Missouri and pockets of the country that are enduring localized outbreaks — conditions that the nation has previously seen at some of the virus’s worst peaks over the last year, before vaccines were widely available.

Increasing data continue to support that vaccines, particularly Pfizer, Moderna and Johnson & Johnson, which have been authorized for emergency use in the U.S., are largely effective at preventing severe illness and death, even against the delta variant, Fauci said during Thursday’s briefing. Hours later, Pfizer announced they would ask the FDA to approve a third booster shot developed to improve immunity against the delta variant. The CDC and FDA later issued a joint statement, saying people who are fully vaccinated do not need boosters and adding, “We are prepared for booster doses if and when the science demonstrates that they are needed.”


Chart by Megan McGrew and Laura Santhanam/PBS NewsHour

Some adults say they need to be able to take time off of work to either get vaccinated or recover (something the Biden administration has worked to address through recent tax incentives for employers) and Jha said they will require different policy tools and interventions than others who choose to go unvaccinated for reasons motivated by politics or misinformation about the vaccines and virus.

Those who are dangerously vulnerable to this variant are not limited to those unvaccinated by choice or access, but also include those who are not yet old enough to get their shots.

Children younger than age 12 should continue to take precautions, such as wearing masks and social distancing, Maldonado said. While communities and households are primary places for transmission, she said that children will be carrying that exposure with them into the classroom. On Friday, the CDC announced that vaccinated teachers and students could go maskless inside school buildings. Questions surfaced about how that policy change might be enforced, including how school administrators might check vaccination status of students.

What’s next?

For the coming weeks and months ahead, Frieden warned of a dynamic we’re already seeing: “a tale of two countries — vaccinated and unvaccinated.” COVID-19 infections will remain low, with occasional upticks, in highly vaccinated places. But in communities where most people remain unvaccinated, Frieden said, “you’re already seeing much higher rates — five, 10, 20 times higher.” He noted that’s lower “compared to the deadly spring,” but that cases are increasing rapidly.

“What the delta variant does is it shortens the fuse between the beginning of spread and explosive spread,” Frieden said.

“This variant is like tinder sitting in a dry forest” waiting for a spark among the unvaccinated, said Dr. F. Perry Wilson, an epidemiologist who directs the Clinical and Translational Research Accelerator at the Yale School of Medicine.

In this phase of the pandemic, the concept of herd immunity has become hyperlocal, he added. Even if the national numbers are looking good, it obscures how vulnerable some counties remain to devastating outbreaks. For people who are vaccinated but live in areas where most of their neighbors are not, Wilson recommended wearing a face mask when indoors with others.

That can be particularly problematic in rural parts of the country, where the health care system was already stretched thin even before the rise of COVID-19. In parts of Missouri or Arkansas, where roughly a third of people are vaccinated, Wilson said the increased transmissibility of the delta variant, and others that may mutate and ascend to take its place, could further overwhelm rural hospitals.

Wilson said he doubts any state has the ability to continue micromanaging outbreaks at that level.

“The best choice you can make for yourself is vaccination,” he said.

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