Dallas County finally hits herd immunity
But even at an 80% threshold, experts warn of new variants
Staff Writer

Dallas County crossed a major threshold this week in its fight to curb the coronavirus pandemic, reaching herd immunity on July 4, according to a nonprofit that tracks health data for the county.

At least 80% of the county’s residents either have natural immunity from previously contracting COVID-19 or are vaccinated, officials at the Parkland Center for Clinical Innovation said in a statement Wednesday.

While celebrating the public health goal, officials at the center and elsewhere stressed continued caution as new strains of the virus — especially the delta variant — continue to take hold here and vaccination rates remain stagnant.

“Reaching the 80% herd immunity rate is not like flipping a switch, but a continuum in our journey,” said Steve Miff, the center’s CEO. “It is an important accomplishment, which is a credit to the residents and public health leaders who have committed themselves to crush COVID.”

Herd immunity occurs when more than 70% of a population has protection either from vaccinations or past infection, according to public health experts. Herd immunity does not mean the coronavirus is eliminated or that infection stops. However, such a milestone should lead to a dramatic end to an infectious disease. But public health experts have also stressed that herd immunity is “fluid” because viruses can mutate and become resistant to existent vaccines.

The center estimates that nearly 49% of the county’s population of 2.6 million residents has natural immunity after recovering from COVID-19. The calculation is based on COVID-19 test results since the beginning of the pandemic. The center assumes that for every positive test recorded in Dallas County, four other adults or five other children also had the virus.

Cases still ticking up

Dallas County has seen a dramatic decrease in new cases and hospitalizations since they peaked earlier this year after the winter holidays. But cases and hospitalizations have ticked up and are holding steady, Dr. Philip Huang, the county’s health director, said earlier this week. On Wednesday, the North Texas hospital region had the highest number of COVID-19 patients in beds since the spring.

“The numbers are still relatively low, but it is concerning,” Huang told county commissioners at a meeting Tuesday.

The delta variant is predicted to make up about a quarter of all new COVID-19 cases locally, doubling about every two weeks, the center said. And given its more infectious nature, the variant could jeopardize the county’s herd immunity status. Nearly 90% of the county may need immunity to suppress a spike in the delta variant.

Varies by ZIP code

Herd immunity is also not uniform across Dallas County: 49 ZIP codes are above the 80% threshold but 45 are still below that mark, according to PCCI.

Among the ZIP codes with at least 80% immunity, nine have 100% protection. Those ZIP codes include most of central Dallas, including 75201, 75202 and 75207. Other ZIP codes include North Dallas’ 75251 and southern suburbs of Seagoville’s 75159 and Sunnyvale’s 75182.

The ZIP codes with the least amount of protection, PCCI said, include north Lake Highlands’ 75243 and Red Bird’s 75237.

Dr. Jamboor Vishwanatha, director for the HSC Texas Center for Health Disparities in Fort Worth, said wide gaps among ZIP codes continue to leave Dallas County vulnerable.

“Herd immunity is not a uniform distribution,” said Vishwanatha, who had not reviewed PCCI’s data. “While we can take an average for an entire county or city, there is still a lot of work to be done either because of access or hesitancy. We should not go based on an average number. If there are ZIP codes that have not reached 50%, we’re all still at risk.”

Only eight Dallas County ZIP codes have less than 50% protection, according to PCCI. And several of the ZIP codes are split with other counties.

Vishwanatha was not surprised that protection lags in some of Dallas County’s more white and affluent neighborhoods.

A political issue

While a dearth of access and community outreach has made it challenging to inoculate Black and Latino communities, the vaccine has become a political wedge issue. And new national research suggests young adults are also a key demographic that is not seeking out the vaccine.

“It may not fall exactly on the socioeconomic line, but it’s still playing a role,” Vishwanatha said.

Dallas County’s inoculation rate continues to remain flat, the center’s data shows. Less than 40% of the total population is fully vaccinated, and less than 50% has received one dose.

Job isn’t over

“While previous infections and partial vaccinations do provide a level of protection,” said Miff, the center’s CEO, “all evidence suggests that full vaccinations are the most effective way to stay safe against the delta variant.”

Locally, less than 1% of those vaccinated have tested positive for COVID-19.

Dallas County Judge Clay Jenkins said Wednesday that the county’s job of vaccinating the public is not over, even as the county health department is expected to shutter its Fair Park mega vaccine site on July 17.

“We’re going to be working door to door, incentives and pop-up clinics — every day, today, tomorrow and every other day,” Jenkins said.

Twitter: @nicgarcia