greg abbott
CNN  — 

Texas Gov. Greg Abbott has been touted as a hero of the Trump conservative movement for his decision, contra science, to end the mask mandate in his state last month and open all businesses at 100% capacity.

That decision, coupled with the fact that Covid-19 cases in his state are largely flat over the past several weeks, are proof-positive to some conservatives that government involvement in mitigating the virus was not only onerous but also, ultimately, sort of pointless.

Whether Abbott has been lucky or good is very much up for debate – especially following an interview on Sunday with “Fox News Sunday” anchor Chris Wallace in which the Texas governor seemed to have little idea (and that is being generous) about herd immunity against the coronavirus actually works.

Here’s the exchange:

Wallace: “Real quick, do you think that you have herd immunity in Texas now?”

Abbott: “When you look at the senior population, for example, 70 – more than 70% of our seniors have received a vaccine shot, more than 50% of those who are 50 to 65 have received a vaccine shot. 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.”

There’s a lot of wrong assumptions in Abbott’s answer here. Let’s go through them.

He says that 70% of people 65 and older and more than half of people ages 50-65 “have received a vaccine shot.” Which is great! But here’s the thing: Full immunity doesn’t arrive after a single shot. In the case of the Johnson & Johnson vaccine, it’s two weeks after the single-dose shot when you can be considered to be fully vaccinated. With the Moderna shot, it’s two weeks after you get the second shot – which is a month after you get your first. With the Pfizer vaccine it’s two weeks after the second shot, which is three weeks after the first one.

(Worth noting: According to Texas public health data, fewer than 1 in 5 Texans (19%) are fully vaccinated; roughly 1 in 3 (32%) have had at least one shot.)

So Abbott is wrong – or at least misinformed – when it comes to understanding what full immunity is and when you get it.

But that lack of knowledge pales in comparison to Abbott on herd immunity in Texas: “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.”

Uh …

So, to sum up: 1) Abbott doesn’t know what herd immunity is and/but 2) he’s pretty sure that Texas “could be very close” to it.

Yeah, that checks out.

Here’s what herd immunity actually is, according to Dr. Christopher Murray, director of the University of Washington’s Institute for Health Metrics and Evaluation. “Herd immunity is the point where there’s enough people that have been either infected or vaccinated that you basically can’t sustain transmission in the community. And if one case leads to less than one new infection, then eventually it peters out.”

Estimates vary on how much of the population would need to be vaccinated – or have the antibodies from a previous coronavirus infection. Some – including Dr. Anthony Fauci -- have pegged that number at between 70% and 85% of the population. Other experts say that number is higher – nearer to 90% of the population.

The point is that Texas – given its current vaccination numbers – isn’t close to herd immunity just yet. That is, unless you believe that well over half of the state’s citizens have has Covid-19. Which, again, is not borne out by the data. According to Johns Hopkins University, Texas has had 2,827,153 confirmed coronavirus cases. That’s just under 10% of its 2019 population (29 million).

Do the math and you get this: Roughly 3 in 10 Texans could currently have some degree of immunity against the virus. That’s less than half of even the low-end estimates of what you would need to achieve herd immunity. Also keep in mind that herd immunity is based on all ages, not just adults – and certainly not just seniors.

Then there’s this: Calculating herd immunity by state is pointless. States aren’t locked down. People travel across state lines all the time. That fact makes it almost impossible to ever declare a state had herd immunity. The only way you could make such a declaration is to close the border of the state – allowing no one in or out. Which Texas isn’t doing.

Abbott isn’t a doctor or an epidemiologist. So, I get that he might not have been entirely clear on the whole concept of herd immunity when the pandemic started more than a year ago. Or even when the first vaccines started to roll out. But when you are the governor of a state that has 29 million people in it, you have a responsibility to bone up on it. And not go on national TV and make ridiculous and wrong claims about where your state is on the march to herd immunity.