John Locher / AP
In this Feb. 10, 2021 photo, people receive a COVID-19 vaccine at the Martin Luther King Senior Center in North Las Vegas.
Thursday, March 25, 2021 | 2 a.m.
Nevada hasn’t achieved herd immunity against COVID-19, but it’s close enough to be characterized by one leading state public health official as “herd dulling.”
Mark Pandori, director of the Nevada State Public Health Laboratory in Reno, estimated that about 30-40% of Nevadans are immune because they have naturally acquired antibodies, which become present by catching the virus. As vaccinations continue, that could bring the state to the ideal level of protection of about 70% within a couple of months, he said.
According to data from the state Department of Health and Human Services, about 24% of Nevadans have received at least one shot as of Tuesday. The first vaccines came to Nevada in mid-December in limited amounts for health care workers, and are set to open up to the adult general public on April 5.
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UNLV epidemiologist Brian Labus said the closer to 100% immunity the better, but that’s not always feasible with human behavior.
“The concept of herd immunity works well on paper. It’s a lot trickier in reality because if we model the whole thing that assumes that every person has an equal chance of coming into contact with every other person in the population,” he said. “Obviously, that’s not the way the world works.”
Herd immunity requires several moving parts — caveats like the known unknowns of how many people had undiagnosed infections, reinfections, and the knowledge that the vaccines are not 100% effective. Epidemiologists also make complex calculations based on virus characteristics — how efficiently it spreads, for example.
That means virus variants could derail Nevada’s progress, but at least so far, the most frequently seen variation — variant B.1.1.7, known colloquially as the U.K. variant — has been shown in recent studies to face resistance from natural and vaccine-induced antibodies, despite being more easily spread.
So where does that position Las Vegas in the midst of spring break, which comes as state mandated occupancy restrictions are relaxing in casinos and other public places?
Not necessarily at higher risk, and that’s not in spite of but because of the visitor turnover in what is currently a weekend getaway, Labus suggested.
“The churn of visitors is interesting because even though everybody says they’re bringing us new diseases all the time, they’re also leaving every three or four days and whatever they’re infected with, they’re taking with them,” he said. “It makes it hard for an outbreak to really spread in a tourist population, because by the time people will develop the disease, they’re on their way home.”
Workers on the Strip with close contact to the public might be at higher risk, but casinos have some mitigating measures, such as plexiglass dividers at table games and mask requirements.
And those visitors just aren’t here very long.
“The system is basically flushed out every few days so that’s why we don’t see these huge outbreaks, and that’s why Vegas looks like every other place when it comes to most of these respiratory diseases,” Labus said.
Pandori said there could be a localized uptick in disease with the revival of tourism, but with so many hostile hosts, a corresponding return of disease might not be sustainable.
He said anyone wondering why Nevada is seeing such a nosedive in cases — the test positivity rate was 4.6% as of Wednesday — can look at the reduced number of hosts for the disease, the fewer opportunities for traditional gatherings since the winter holidays, and continued mask-wearing for what he called the “herd dulling.”
“I think there’s something real going on here, and I think if it’s not herd immunity it’s this contribution of having very much fewer targets available for the virus, and it’s probably causing a kind of dulling effect on the spread of the virus,” Pandori said.
He cautiously anticipates a gradual slide into herd immunity by the end of summer, but said vigilance is still necessary even as the virus’ rampage appears to be diminishing. This is when the work of masks and distancing can be even more apparent.
“It’s not party time. It’s finishing time. It’s the part in the gladiator arena when the emperor says, ‘Show no mercy to this opponent,’” he said.
The Southern Nevada Health District also lauded the progress but encouraged Nevadans to continue taking precautions.
"It will take a combination of more people getting vaccinated, along with people continuing to wear masks and social distancing as much as possible when they are in public to continue these positive trends," it said in a statement.
Pandori suggested another applicable analogy, which he said is even better: the campfire.
Hours after a campfire has quieted down, flames have been reduced to coals. But the coals are still hot and if ignored, the wind could still pick up embers and reignite the fire that spreads through the forest.
“You pour water on it and you bury it. That’s how you win,” Pandori said. “It’s exactly the same thing.”
