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Rising COVID-19 cases among unvaccinated Arizonans causing more infections among vaccinated

The average number of COVID-19 cases reported daily in Arizona has risen more than 25% in the last two weeks. The surge is driven by people who aren’t vaccinated, but breakthrough infections among vaccinated people appear to be on the rise too.

According to the Arizona Department of Health Services, about one in five COVID-19 cases in Arizona in October was a breakthrough infection.

Dr. Joe Gerald talks about breakthrough cases with host Lauren Gilger on The Show


"The vaccines do a phenomenal job at preventing hospitalization and death due to COVID-19. In most cases it also prevents illness, but not in all cases," said Jessica Rigler, assistant director for the division of public health preparedness with the Arizona Department of Health Services.

Rigler said with the virus so widespread in the community, vaccinated people will simply come into contact with the disease more. 

“You’ll see more opportunities for people to be exposed and then to potentially become infected," Rigler said. 

According to the Arizona Department of Health Services, 82% of COVID-19 hospitalizations and 83% of COVID-19 deaths in October were among unvaccinated people. That's a decrease from August, when unvaccinated people made up 87% of the state's hospitalizations and deaths.

Months after the first vaccines were administered, immunity is beginning to wane for some vaccinated people, which could be contributing to the increase in breakthrough infections, said Dr. Joe Gerald with the University of Arizona's Zuckerman College of Public Health. Gerald said vaccines still effectively protect against serious illness or death after several months but may not provide enough protection to stop the virus from spreading altogether.  

“Now we’re at a point where it’s looking like pretty much everybody is going to need [a booster shot] to achieve the level of immunity necessary to keep this tamped down," Gerald said.

The Centers for Disease Control and Prevention currently recommend  booster shots for anyone initially vaccinated with the Johnson & Johnson vaccine or high risk individuals who had the Pfizer or Moderna shots. 

While boosters are important, Gerald said ultimately, Arizona needs more unvaccinated people to get their first shots. About 54% of Arizonans are fully vaccinated,  according to the CDC. The national rate is 59%. 

As cases among unvaccinated and some vaccinated Arizonans increase, Gerald said the state also needs to do more to limit crowd sizes and encourage indoor mask use.

“Some parts of the country are doing very well at maintaining those types of measures. Here in Arizona, we’re not doing very well at all," Gerald said. "We could be doing more, but we’re not." 

Arizona Coronavirus Cases, Deaths

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Katherine Davis-Young is a senior field correspondent reporting on a variety of issues, including public health and climate change.