Over half of Denton County’s vaccine-eligible have received a COVID-19 shot: Is herd immunity on the horizon?

Richardson cited vaccination data from the Texas Department of State Health Services, which tracks totals both for the state and for each county. Richardson noted that for Denton County, over half of its 16-and-older residents are at least partially vaccinated.

As of Tuesday afternoon’s data update following the meeting, DSHS estimates 374,588 county residents have received at least one shot. With an estimated 697,330 residents ages 16 or older, that comes out to 53.7% of the county’s vaccine-eligible population having received a dose. Additionally, the department estimates 41% of that age range has been fully vaccinated.

Following a question from Precinct 4 Commissioner Dianne Edmondson, Richardson addressed the county’s path to herd immunity. An exact number for herd immunity could be anywhere between 70% to 95% of the population having either been previously infected with the virus or vaccinated — but measuring that mark, he said, is laced with challenges.

“If you speak with epidemiologists and statisticians in public health, 70% is the beginning to where the transmissibility is impeded,” Richardson said. “Here’s the problem calculating herd immunity: We don’t know exactly how many people in Denton County have gotten COVID-19.”

Richardson explained that Denton County Public Health knows only the number of people who have tested positive for the coronavirus — not the total number of county residents who have been infected, which includes many who either were ill and did not get tested or were asymptomatic. He said research estimates the number of reported cases, about 75,000 for the county, could be multiplied by 3 to get what’s likely a more accurate, but still inexact, picture.

The other part of the herd immunity equation, the vaccination total, also has a glaring issue: The county does not know how many vaccinated residents had previously contracted the virus. Richardson said this prevents DCPH from simply combining the number of vaccinated residents with the number of cases.

“You can’t really add those two numbers together, which is very commonplace … it’s more complicated than that,” Richardson said. “We’re not going to have a precise number, so the best way to estimate herd immunity is to see how many people in the herd are sick. As that number decreases, more and more shots build with more recoveries, and we know we’re getting a lot closer.”

Edmondson asked Richardson directly if he could put a date on reaching herd immunity, referring to Dallas County’s recent estimate of late June or July. He declined to do so, stating multiple assumptions and projections were used in Dallas’ estimate.

“It’s really three projections to come up with a date,” Richardson said. “I have to tell you, I’m probably not comfortable trying to replicate that.”

So what’s next in the county’s vaccination timeline? Despite initially aiming to hold its final first-dose clinic at Texas Motor Speedway over a week ago, Richardson said two more such clinics are planned for this Saturday and next Friday before it closes up shop at the speedway. After finishing up there, he said DCPH operations will move elsewhere in the county, with a focus on vulnerable populations.

That shift, Richardson said, could coincide with the Pfizer vaccine being approved for children as young as 12. He said he anticipates the Food and Drug Administration approving that expansion for the Pfizer shot, currently only COVID-19 vaccine authorized for teens ages 16 and 17, in the coming weeks. At that point, Denton County could begin hosting clinics at schools to vaccinate the newly eligible children and anyone else who has yet to receive their shot.

County Judge Andy Eads said that in recent weeks, officials have met with school superintendents, who have offered to open their campuses up for use as vaccine clinic sites. He said the county would primarily use high schools as clinic sites next month, after school lets out for the summer.

“We’re going to be taking a neighborhood approach as we reach out to all four corners of the county,” Eads said. “When school’s out, we’ll be rolling into the campuses. … It will not be the large, drive-thru concept like we have at Texas Motor Speedway. It will be a smaller, walk-in style approach in school cafeterias and gymnasiums.”