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Talk of 'herd immunity' alarming for UA COVID-19 researchers

Talk of 'herd immunity' alarming for UA COVID-19 researchers

Tucson researchers following Arizona’s COVID-19 trends are bracing against the renewed push for “herd immunity” by the Trump administration.

Most Arizona residents, like people in much of the country, do not have antibodies for the virus yet, and those who do can’t count on how long they will be protected against reinfection.

Antibody tests in recent weeks show a statewide positivity rate of about 10%, according to Arizona Department of Health Services data, while University of Arizona researcher Dr. Joe Gerald finds it closer to 12%. The positivity rate including all tests statewide since the pandemic began is around 7% while UA testing shows it’s about 4% in Pima County.

Regardless of the exact numbers, this means one thing to Dr. Janko Nikolich-Zugich, head of the UA’s Department of Immunobiology: Roughly 90% of Arizonans have not been exposed to the virus, and are therefore vulnerable.

“It follows that it remains critically important to follow all public-health precautions on distancing, mask-wearing and hygiene, at least until we get a reliable and efficacious vaccine,” said Nikolich-Zugich, also co-director of the UA’s Center on Aging.

Herd immunity, as an alternative to following precautions during a pandemic, happens when enough people get the disease and become immune to stop it from spreading.

A national petition from early October called ‘The Great Barrington Declaration’ calls for “focused protection” that would allow the reopening of businesses and schools, among other measures. The New York Times reported the Trump administration has embraced at least aspects of this approach, which would entail letting the young and healthy get sick while trying to protect older people and those more vulnerable to the worst of COVID-19.

“If we were just talking about the common cold, who cares? It’s not like that has tremendous (public health) implications. But for diseases with severe health consequences, it’s not something to be taken lightly,” said Dr. Joe Gerald, associate professor of public health policy and management at the UA’s Mel and Enid Zuckerman College of Public Health.

“We want to reach herd immunity, yes, but we want to do that through vaccination.”

“Positivity rate not changing much”

At the height of the antibody, or serology, testing in Arizona over the summer, about 5,000 tests were being carried out each day. Now, there are only about 1,000. The reason, Gerald said, is that clinicians and patients alike were not finding the results very helpful.

“The positivity hasn’t been changing much since July even though we know the number of cases in Arizona continues to climb,” he said. “What we would normally expect is that the serology positives would increase.”

What’s needed to understand why, he said, is more data.

The primary costs to carry out a more comprehensive study would be blood draws and getting the word out, said Bonnie LaFleur, a research professor of biostatistics at the UA’s Bio5 Institute.

LaFleur couldn’t provide an estimate quickly but said UA researchers are uniquely poised to do such a study both cheaply and effectively. There are already mobile health units in circulation, she said, and quite a few sites are set up for blood draws for antibody testing already.

Taking all of that into account, she believes that for under $500,000, they could do a representative sampling of Pima County residents and accurately estimate antibody prevalence here.

‘“For the sake of the community”

For people who test positive for antibodies, Gerald said there should be a “reasonable expectation of immunity for four or five months,” but that shouldn’t change the person’s behavior.

The reason is that, in addition to not knowing how long the antibodies will last, it’s also critical for everyone to keep modeling safe practices for the sake of the community, he said.

“When we look at some of the other coronaviruses, we know immunity is not lifelong,” he said. “We don’t know yet where COVID-19 is going to fall on the spectrum.”

For Anne Poulin, a registered nurse at St. Mary’s Hospital, following health protocols is her focus for keeping herself and others safe. So far, she’s had two negative antibody tests and four negative COVID-19 tests since she started treating coronavirus patients seven months ago.

She is not a fan of the push for herd immunity.

“I assure you, having been coughed on thousands of times, and taking off and on (breathing) machines and high-flow oxygen on COVID patients for eight months, masks do work,” she said.

Contact reporter Patty Machelor at pmachelor@tucson.com or 806-7754. On Twitter: @pattymachstar

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