“We remain very vigilant and guarded and proactive in our response, but there is simple math behind the reason why we continue to have success,” Abbott, a Republican, said on “Fox News Sunday.” The equation “means, very simply, it’s a whole lot more difficult for covid-19 to be spreading to other people in the state of Texas.”
Experts have said that immunity from vaccinations and prior infections may have partly contributed to declining cases nationwide after the virus’s winter surge. But in Texas, the numbers Abbott cited don’t add up to herd immunity, according estimates of that threshold.
Scientists don’t know the precise point at which herd immunity will begin, but in recent months they’ve said anywhere from 70 percent to more than 90 percent of the population would need to acquire protection. Anthony S. Fauci, the country’s top infectious-diseases doctor, has predicted 80 percent to 85 percent.
Lauren Ancel Meyers, a biology professor at the University of Texas at Austin and director of its covid-19 modeling consortium, said that “a lot of misinformation and misunderstanding” has surrounded the herd immunity threshold and that several factors could still influence it.
“It depends on the efficacy and duration of immunity acquired through infection or vaccination, whether we have pockets of low immunity in our communities and whether there are emerging variants that can evade immunity,” Meyers said.
Just 19 percent of Texas residents are fully vaccinated, according to figures from the Centers for Disease Control and Prevention, a lower share than all but six U.S. states. Health officials there have confirmed more than 2.4 million infections and counted an additional 400,000 “probable” virus cases. Almost 50,000 of those people have died, according to data gathered by The Washington Post.
The official number of people who have survived infection — about 2.77 million — plus the number inoculated — about 5.5 million — equals more than 8.27 million people with some form of immunity, or about 29 percent of Texas’s population.
However, there is a hidden variable that is crucial to this calculation: the number of people who have contracted the coronavirus but have not been formally counted — either because they were never tested or were never linked to a positive case.
It is impossible to know exactly what this number is, but researchers reckon that it’s much greater than what shows up on state data dashboards and the ubiquitous pandemic trackers. A team at Columbia University used a mathematical model to estimate the true scope of infections, and it found that by late January, 31 percent of Texans probably had contracted the virus.
This would mean at least 50 percent of residents have some sort of immunity — more than the official tallies would suggest, but still well short of Abbott’s pronouncement.
Jeffrey Shaman, the study’s lead researcher, added a note of caution when discussing his findings with NPR: Protection gained through mild or asymptomatic infection may wane and offer little help in the race to herd immunity, he said.
In his Fox News interview, Abbott said that more than 70 percent of the state’s seniors received at least one dose of a vaccine and more than 50 percent of those ages 50 to 65 have gotten one.
“I don’t know what herd immunity is, but when you add that to the people who have acquired immunity, it looks like it could be very close to herd immunity,” he said.
Last week, the epidemiologist Michael T. Osterholm predicted the beginning of a “fourth surge” of new cases, pointing to hot spots in the Midwest and the pattern of previous pandemic waves, which tended to hit northern states before moving south. His message was clear: In due time, case numbers will rise in states such as Florida and Texas.
In an interview with the New York Times on Sunday, Osterholm reacted bluntly to Abbott’s boast: “There is no way on God’s green earth that Texas is anywhere even close to herd immunity,” he said.
The governor has touted the state’s trends as evidence that his aggressive reopening strategy, which public health experts criticized, is working. In the month since Abbott lifted the state’s mask mandate, the daily average of newly reported cases has decreased from 4,700 to about 3,500. In March, scholar Daniel W. Drezner wrote in an essay for The Post that the politicization of herd immunity is “inevitable,” with scientists revising their threshold estimates upward and conservative commentators contending it is lower.
But such arguments could be costly, with experts pointing to virus variant-driven outbreaks in states such as Michigan and Minnesota as evidence that the country is not yet in the clear. Both Midwestern states have vaccinated a higher share of their populations than Texas — 24 percent in Minnesota and 22 percent in Michigan — yet they’ve been unable to escape the latest surges.
“We don’t know if and when we’ll get to the point that the virus is completely eliminated, particularly given complications like emerging variants and pockets of low vaccination coverage,” said Meyers, the UT biologist. “Still, the closer we get to herd immunity by closing gaps in vaccine coverage and overcoming vaccine hesitancy, the safer, healthier and more open our society will be.”