PHOENIX (3TV/CBS 5) - Almost 250,000 Arizonans have gotten at least one dose of the COVID-19 vaccine, but that puts us quite a ways off from the 5 million or so we need to reach to achieve herd immunity in our state.

Simple math says that if a quarter of a million people get the vaccine each month, it will take more than a year and a half to get 70% of the state’s population protected (the percentage needed for herd immunity). However, an infectious disease expert says several factors will help us reach the end goal much sooner than that. Thousands of people 65 and older got frustrated when they tried to register for a vaccine appointment Tuesday, the first day they were available.

“When I refreshed this morning, it wasn’t doing anything,” said Kathleen Segar of Mesa, who jumped online as soon as the state announced time slots were available for her age group.

The website was so bogged down she gave up after six attempts, though she finally got a late-February appointment hours later.

“It just feels like we’re underwater,” she said. “We’re not making forward progress that I was hoping by now, a year into this; we would be.”

Mayo Clinic’s Infectious Disease Virology Lab Director Erin Kaleta says we’re not as underwater as you might think. Though many people have been vocal about a slow start to the vaccine rollout, she says it won’t stay that way.

“It’s starting to ramp up. Every week we start allocating a little bit more and vaccinating more patients,” Kaleta said.

For months we’ve heard summer 2021 as the time we might hit herd immunity, and Kaleta says that goal is still within reach. One reason is that, in addition to the vaccinations, the almost 700,000 Arizonans who have already been infected with COVID-19 also create a buffer on the population.

“They’re both working towards the same goal of having those antibodies and having that immunity – that protective immunity,” Kaleta said.

Mayo studies have found the number of infections may actually be 3 to 4 times higher than test results show, so it’s possible we could be halfway to our target of 5 million and not even know it. However, the difference between antibody protection from infection and from vaccination is that each person gains a different level of immunity to the virus depending on how severely it affects them. That’s why Kaleta has further advice.

“Even if you’ve had a prior infection, you should still get vaccinated,” she said.

Additionally, Kaleta says If we can keep COVID reproduction rates down, we won’t need as high of a percentage of people vaccinated to get herd immunity. That’s why it’s still important to wear masks and keep your distance from others even after you’ve gotten your shots.


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