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Arizona unlikely to beat back new virus variants, but next surge could be less deadly
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Arizona unlikely to beat back new virus variants, but next surge could be less deadly

COVID-19 vaccinations, UA

Linda Wills, 71, receives her first vaccination shot at the University of Arizona in Tucson, Ariz., on February 10, 2021. The university will serve as the state’s first 24/7 vaccination site in Southern Arizona, dramatically increasing vaccinations across the Tucson metro area starting on Feb. 18.

Arizona’s top health official expects a new, more contagious coronavirus variant to take over Arizona by April.

The state is in a race against these variants to distribute as many vaccinations as possible before this happens.

“These viruses are so hard to predict especially with as much mutation that they do,” Arizona Department of Health Services Director Dr. Cara Christ said.

Two new, more contagious variants have been detected in Arizona and their numbers are growing. One came from the United Kingdom, which is also known as B.1.1.7. The other originated in Southern California, also known as B.1.427 or B.1.429.

Arizona likely won’t reach herd immunity before one of these variants take over, but health-care workers will likely vaccinate enough people so that another wave of cases would be less severe.

Across Arizona, about 2.8% of the population has received both vaccine doses, according to data from the Centers for Disease Control and Prevention as of Friday.

This percentage ranked 47th among all states, territories and the District of Columbia — a group of 59 places. At the same time last week, Arizona ranked 50th. West Virginia was the highest ranking state on Friday, coming in third with 6.7% of its population fully vaccinated.

a moving target

While fighting the current coronavirus variant in Arizona, the state needs to reach about 65% immunity statewide to achieve herd immunity and stop the virus, said Dr. Joe Gerald, an associate professor with the University of Arizona’s College of Public Health. But he added that we might need to reach around 80% immunity when a new, more contagious variant takes over.

Herd immunity will happen with some combination of natural immunity and vaccinations. Gerald has estimated that 30% to 33% of the population already has some natural immunity.

This would mean the state would need to vaccinate north of 30% of the population if we were to only fight the current variant, but we’ll need around 50% vaccinated once a more contagious variant takes over.

These estimates have a few limitations. First, other estimates of natural immunity are lower. And the Centers for Disease Control and Prevention is still learning about reinfections, but some such cases are expected.

Also, Pima County Health Department Director Dr. Theresa Cullen warns that we don’t know the longevity of immunity. This makes it difficult to calculate the true number of naturally immune people.

Ultimately, Gerald said, we won’t know the exact numbers needed to reach herd immunity until we have the benefit of hindsight.

The Biden administration will begin providing COVID-19 vaccines to U.S. pharmacies, part of its plan to ramp up vaccinations as new and potentially more serious virus strains are starting to appear.

“The more people we vaccinate, the better”

Using these estimates as a guide, however, can at least give us an idea of what we’re up against.

Christ said health-care workers are administering about 215,000 vaccine doses a week across the state, adding that this rate will accelerate as times goes on.

So far, Arizona has given at least one dose of the vaccine to about 10.7% of the population, according to CDC data, as of Friday.

Christ estimated that it will take about four more weeks to give at least one dose to 20% of the population. And it may take eight weeks to reach 30% of the population.

And she said administering both doses may lag four to five weeks behind that. This would mean the state would have 30% of the population fully vaccinated by sometime in May, which is after Christ expects a more contagious coronavirus variant to take over.

While this falls short of the reaching the estimated 80% total immunity needed to achieve herd immunity, it doesn’t necessarily mean the state will have lost the race against the more contagious variants.

It’s hard to define how the state could win or lose this race, said Dr. Joe Gerald, an associate professor with the University of Arizona’s College of Public Health.

“There’s no obvious threshold or numerical value that would distinguish between winning and losing,” Gerald said.

It’s a more relative distinction between doing a better or worse job, he said,

In light of vaccine hesitancy, herd immunity is an important goal to work toward, but it’s not the most important concept right now, he said. Instead, the more people we vaccinate, the better, especially those who are most vulnerable.

“Our health-care system is now safe”

Thousands of people will become infected between now and next fall, he said. The goal is to prevent as many hospitalizations and deaths as possible.

We may see another surge in cases this spring tied to a new variant, but the consequences might be less dire than previous surges.

While a more contagious coronavirus variant would make it harder for Arizona to reach herd immunity, Gerald said he thinks the type of outbreak that brings the state’s health care system to its knees is likely behind us.

“I think our healthcare system is now safe,” he said. “It’s actually very very busy right now, but we’re on the downswing. Our vaccination rollout has prioritized those over the age of 65, more or less, and those are the individuals who are at greatest risk of being hospitalized and dying.”

Even if we have a resurgence of cases, he said, we will likely not have the same number of severe or deadly cases as we have during previous spikes.

“There’s just too many people who are now immune, either from infection and recovery or vaccination, that that size of an outbreak is no longer sustainable based on the epidemiology,” he said.

Hospitalizations and deaths on the decline

All major COVID-19 metrics are trending in the right direction, signaling that conditions are improving in hospitals and the virus is spreading less.

Statewide, weekly totals of new cases dipped below the summer peak for the first time since the second week of November, according to ADHS data, as of Friday.

Week-to-week cases decreased across the state by 36% to 18,129 in the first week of February, while diagnostic tests fell by 12%. And the percentage of positive diagnostic tests fell from 16% to 12%.

In Pima County, weekly totals of new cases recently about matched the summer peak.

Week-to-week cases decreased across the county by 34% to 15,025 in the first week of February, while diagnostic tests fell by 20%. And the percentage of positive diagnostic tests fell from 14% to 11%.

New hospitalizations and deaths also declined in the first week of February, according to data published by state and county health departments.

Contact reporter Alex Devoid at adevoid@tucson.com or 573-4417.

On Twitter: @DevoidAlex


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Data/Investigative Reporter

Alex has been with the Star since June 2019. He previously wrote about the environment for the Arizona Republic and he's a graduate of the University of Arizona.

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