Recent data from Yavapai County Community Health Services suggests that COVID-19 vaccines are effective at blocking infec­tions and serious illness amid the current wave in Arizona, but the protec­tion may be waning for the earliest recipients of the vaccines.

Overall, in the last 28 days, unvaccinated residents made up 87.5% of new COVID-19 cases in people age 13 and over, or 1,723 of 1,968 new cases.

The data suggests the vaccines have been even better at preventing serious illness: 90.4% of people recently hospitalized with COVID-19 in Yavapai County were unvaccinated.

Terri Farneti, public health coordinator for Yavapai Community Health Services, said the data shows vaccines are preventing infection and serious illness, even as the more-contagious Delta variant has become predominant in Arizona.

Though breakthrough infections are a small minority of COVID-19 infections in all age groups, the ratio of breakthrough to unvaccinated infections is highest in the oldest age groups — groups that were among the first in line for vaccinations when they became available.

One interpretation of this trend is that nine months after they were administered first to seniors, the immu­nity has gotten weaker over time.

This is consistent with an Aug. 18 statement from the U.S. Department of Health and Human Services that the agency had found that “protection against SARS-CoV-2 infection begins to decrease over time following the initial doses of vaccination” and “the current protection against severe disease, hospital­ization, and death could diminish in the months ahead, especially among those who are at higher risk or were vaccinated during the earlier phases of the vaccination rollout.”

In the same statement, the HHS announced that it had developed a plan to begin offering booster shots of the Pfizer and Moderna vaccines beginning the week of Sept. 20. The current plan is to make people eligible for boosters eight months after they received the vaccine. The agency said it is also developing plans for boosters of the Johnson and Johnson vaccine, which was released after the Moderna and Pfizer vaccines.

People with moderate and severe immunodefi­ciency are already approved for Pfizer and Moderna boosters, and Spectrum Healthcare announced Aug. 18 that it was offering the booster shot at its Cottonwood clinic and through home visits.

Current Wave

The county is currently experiencing a “high rate of transmission” according to the state metrics, and last week was one of the deadliest weeks in Yavapai County for COVID-19 since the wave of last winter. Between Monday, Aug. 23 and Monday Aug 30, Yavapai County reported 15 COVID-19 deaths and 705 confirmed infections. One of the people who died with a COVID-19 infection lived in Cottonwood.

YCCHS’ Aug. 27 COVID-19 update sounded a more urgent tone than usual.

“COVID-19 is an emerging, rapidly evolving situation. The U.S. is in the grip of a fourth wave of infection this summer, powered by the highly contagious Delta variant, which has sent cases, hospitalizations and deaths soaring again, and erased months of progress against the virus. What COVID-19 has in store for this fall depends on human behavior,” the release stated. “Our behavior is going to determine if, when and how long the current wave lasts, which means doubling down again on masks, limiting social gatherings, staying home when sick and getting vaccinated. We can make choices that reduce risk for ourselves, our fami­lies, children, co-workers, teachers, bus drivers, jani­tors — everyone.”

Yavapai County’s vaccination rates, especially in younger age groups, are below the state average, with 45% fully vaccinated in the county compared to 55% in the state as a whole. The vaccination rates are especially low for younger residents. State data shows that 32% of residents age 20 to 34 are vaccinated in Yavapai County, and 37% of residents 35 to 44.

In August there was an uptick in vaccina­tions in Yavapai County, with between 200 and 500 administered per day, compared to spring vacci­nations numbering between 1,000 and 3,000 daily.

But those looking to herd immunity to alleviate the strain of new infections, sick days and quarantines will have a long time to wait. Adding the total number of people vacci­nated in Yavapai County, 92,396, with the number of reported COVID-19 cases, 23,589, amounts to roughly half the popula­tion of Yavapai County. About 46,000 more people need to survive infection or get vaccinated before the county achieves the low end of the estimated numbers needed for a herd immunity effect, or 70%, where new infections have a hard time spreading in the population.