Spread of delta variant ignites covid hot spots in highly vaccinated parts of the U.S., Post analysis finds

The highly transmissible delta variant of the coronavirus – once concentrated in poorly vaccinated pockets of the United States – is making incursions into even highly vaccinated counties that remain short of herd immunity. One measure of the spread of the variant: hot spots are flaring in these counties.

Two-thirds of people who live in the nation’s most highly-vaccinated counties reside in a place now considered a hot spot, according to an analysis by The Washington Post. The analysis illustrates how rapidly the state of the pandemic changed in July from a problem for the unvaccinated to a nationwide concern, though life in highly vaccinated states is still safer.

The Post classified the highest quarter of counties as high vaccination, with at least 54 percent of the population fully vaccinated. The lowest quarter of counties were classified as low vaccination, with fewer than 40 percent of the population fully vaccinated. The Centers for Disease Control and Prevention identifies hot spots as areas with high and rising caseloads, as compared with areas with moderate or low coronavirus outbreaks.

On the Fourth of July, just 4 percent of residents of highly vaccinated communities lived in hot spots, compared with 13 percent of people in low-vaccination areas. The outbreaks initially grew in the poorly vaccinated areas, where 28 percent of residents lived in hot spots as of July 14, compared with 13 percent of residents in highly vaccinated communities.

The gap narrowed in recent weeks as cases surged in major West Coast cities, South Florida urban centers and the New York-to-Boston corridor. By August, it closed. About two-thirds of residents living in both highly and poorly vaccinated counties are now in hot spots with high and rising caseloads.

Even in communities where at least 70 percent of the population is fully vaccinated, delta is so widespread that 6 in 10 residents are in hot spots.

Their experiences are not the same as those in sparsely vaccinated hot spots. It’s like the difference between being in a trailer and a house in a hurricane: Both might get hit, but one harder than the other.

Living in a hot spot while vaccinated today is much safer than living in a hot spot while unvaccinated last summer. High-vaccination states have one-third the number of new cases per capita that low-vaccination states have.

Hospitalization rates in states with less than 40 percent of their population fully vaccinated are four times those in states that are at least 54 percent vaccinated, The Post found.

Oregon is seeing such differences as hospitalizations reach all-time highs and Portland, in a county where two-thirds are fully vaccinated, is a hot spot alongside sparsely vaccinated rural counties.

“We are dealing with a new foe that’s so much more contagious, so it doesn’t require that high of a percentage of unvaccinated people to spread but it is spreading faster in those parts of the state seeing lower vaccination rates,” said Dean Sidelinger, Oregon’s state epidemiologist. “Those counties with higher vaccination rates have a fairly slow rise in hospitalizations, but the counties with the lower vaccination rates have a much steeper rise in hospitalizations.”

Public health leaders in highly vaccinated hot spots attributed the outbreaks to several reasons.

Even urban areas that can boast high vaccination rates have hundreds of thousands or millions of susceptible unvaccinated residents who are at greater risk of contracting the virus than during earlier spikes because businesses have reopened. Masks are often not required in public, and the delta variant spreads more easily. Well-vaccinated areas are not bubbles: Infected visitors are spreading the virus and residents are traveling to more poorly vaccinated places and getting sick. Breakthrough infections do not appear to be as extremely rare as hoped, accounting for more than a fifth of new recent infections in Los Angeles; New Haven, Conn.; and Oregon, officials said.

“Don’t think just because your county and your city is well vaccinated that this can’t affect you,” said Jennifer Avegno, director of the New Orleans Department of Health. “Do the things you need to do, particularly with schools returning and large festivals happening. Get ready. I hope you are spared, but we didn’t think it would be this bad.”

Louisiana, where fewer than 38 percent of residents are fully vaccinated, is confronting the nation’s worst surge with 120 new daily cases per 100,000 residents. In Orleans Parish, home to New Orleans, 53 percent of residents have been fully vaccinated, but it has still been pummeled during the surge, with 89 new daily infections per 100,000 residents.

“The problem is when you have such a large reservoir of unvaccinated individuals surrounding an island of a highly vaccinated place you are just going to have a lot of transmission,” Avegno said.

That doesn’t mean the city’s vaccination efforts are for naught.

Residents of Orleans Parish have a far lower hospitalization rate at 16 per 100,000 than the statewide rate, 46 per 100,000, according to Covid Act Now data cited by local health officials. But the city’s hospitals are still under strain as covid-19 patients from sparsely vaccinated rural areas that lack quality hospitals arrive for care.

While the city doesn’t have reliable data on the prevalence of breakthrough infections, Avegno suspects they may be common.

She cited the recent CDC study of an outbreak in Provincetown, Mass., where three-quarters of the infected were fully vaccinated, bolstering suspicions that vaccinated people are more easily spreading the transmissible delta variant even in vaccinated communities. More than 1,000 people were infected; seven were hospitalized.

[How Provincetown, Mass., stress-tested the coronavirus vaccine with summer partying and delta]

The study raised concerns among public health officials in highly vaccinated communities about immunized people spreading the virus to vulnerable people, including children under 12, who are not eligible for vaccines.

“We don’t want to begin to see outbreaks in our children,” said Lori Freeman, chief executive of the National Association of County and City Health Officials. “It’s not all about people who choose not to get vaccinated; it’s about the people who simply cannot get vaccinated either.”

Los Angeles County was one of the first to recognize that risk when it urged all residents to wear masks in late June and imposed an indoor mask mandate in mid-July, even though 61 percent of eligible people were fully vaccinated at the time.

Officials cited data from Israel suggesting vaccinated people may be spreading the highly contagious delta variant. Their fears appeared to be well founded: A quarter of July infections were among fully vaccinated people.

“When you don’t know something or don’t know something well, we learned the lesson with covid is you are better off being cautious,” said Barbara Ferrer, director of the Los Angeles County Department of Public Health.

Severe illness among them was rare, with the vaccinated making up about 12 percent of hospitalizations in late July. And fewer than 1 percent of the 5 million Los Angeles County residents fully vaccinated this year have tested positive.

But Los Angeles County health officials credit the universal masking order for helping to control the latest surge, citing slower case growth than in parts of California without mask mandates.

Ferrer said she was wary of California’s June 15 full reopening from the start. Even though vaccinated people as individuals are protected, the communities they live in are not out of the woods when no major jurisdiction has reached the 80 to 90 percent immunity some experts now believe is necessary to protect against delta outbreaks.

“It’s hard to just sort of say at this point without there being community immunity, we are going to be a hands-off operation,” Ferrer said. “The more transmission, the more chance of mutations and the more chance one of these mutations may evade the vaccines.”

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While much of the summer coronavirus surge has been concentrated in the South and around the Ozarks, cities in the Northeast have started to emerge as hot spots.

The CDC last week dubbed New Haven the first Connecticut jurisdiction at high risk for transmission even though it is 62 percent fully vaccinated.

Of the 624 New Haven cases reviewed since July, 22 percent were fully vaccinated. Health Director Maritza Bond said preliminary data suggests the breakthrough cases are disproportionately among seniors and people with preexisting medical conditions that would make it harder for their immune systems to fight the virus, even after vaccination.

The virus also appears to be coming in from elsewhere: 93 of the summer surge cases involved out-of-state travel, including to hot spots like Florida, and 17 traveled internationally.

The city quickly imposed an indoor mask mandate that took effect this week ahead of vaccinated Yale University students returning to campus later this month.

“Yes, it’s tough that we have to wear a mask again. Trust me, I’m not happy I have to wear a mask,” Bond said. “We have to be prudent and really tough it out so we can get through this, and we are not going to get through this until we really reach herd immunity. As a country, we are nowhere near that.”

Fenit Nirappil covers the coronavirus pandemic for the Health & Science team. He previously covered local politics.
Dan Keating analyzes data for projects, stories, graphics and interactive online presentations.
Maria del Carmen Aguilar is a graphic reporter in the graphics department at The Washington Post.
Naema Ahmed is a graphics reporter at The Washington Post. Before joining The Post, she worked at Axios as a data visualization designer.
Aaron Steckelberg is a senior graphics reporter who creates maps, charts and diagrams that provide greater depth and context to stories over a wide range of topics. He has worked at the Post since 2016.