Staff Photo by Matt Hamilton / Nurse Vicki Reinshagen administers a dose of the COVID-19 vaccine to Chattanooga resident Martha Carpenter at the Tennessee Riverpark on Tuesday, Sept. 28, 2021.

Demand for first-dose COVID-19 vaccinations spiked in August and September during the surge of new infections and hospitalizations caused by the delta variant. But as case rates have fallen in the past two weeks, so too have vaccination rates in Hamilton County and throughout Southeast Tennessee.

At the end of September, the rate of first-dose vaccinations in a 12-county area of the state that includes Hamilton County was less than half of what it was in mid-August, according to data from the Tennessee Department of Health.

Dr. Lisa Piercey, commissioner of the Tennessee Department of Health, said during a news briefing last week it was understandable vaccination rates would fall as new case counts decreased.

"We had some really good uptake over the first few weeks of the surge. And so we'll see those people come back for second doses," Piercey said. "We'll still see some continued momentum, but we are down from where we were in the last three weeks."

Vaccination rates fell throughout the summer until the delta variant caused a surge in cases and hospitalizations in August.

Midway through the month, Hamilton County was averaging more than 600 first-dose vaccinations a day, a figure the county had not reported since mid-May.

Although each age group saw an increase in vaccination rates during the latest surge, Hamilton County residents ages 12-15 saw the largest boost, going from just 16.3% of that age group being at least partially vaccinated as of July 1 to 44.2% as of Oct. 1, according to health department data.

Residents ages 16-20 saw the second-largest rate increase, moving from 30.2% at least partially vaccinated on July 1 to 48.3% partially vaccinated on Oct. 1.

The Pfizer vaccine achieving full FDA approval as opposed to emergency use authorization, as well as an increasing number of workplace vaccination requirements and incentives and local vaccine education campaigns, were other factors that likely contributed to a spike in newly vaccinated residents in late summer.

But first-dose vaccination rates have fallen as the delta surge of new cases and hospitalizations fell in recent weeks. Hamilton County averaged 112 new cases a day on Monday, a 69% decrease from two and a half weeks earlier. The county reported 167 people hospitalized with the virus Monday, down from the record high 372 on Sept. 3, according to data from the county health department.

As of Monday, 49% of Hamilton County residents and, as of Sunday, 47% of Tennessee residents are fully vaccinated, both below the national average of 56% of Americans fully vaccinated, according to data from the U.S. Centers for Disease Control and Prevention.

Dr. Ajay Sethi, an associate professor of population health sciences at the University of Wisconsin–Madison, said it's still early to make predictions about the likelihood of another COVID-19 surge in the winter months.

Although cases are trending down in areas of the South hit hard by the delta variant this summer, cases are surging in some Northern states with lower vaccination rates, such as Alaska and North Dakota. Whether the pandemic dissipates or resurges depends largely on the dynamics of the viral variants that are circulating.

"Delta seems to have this two-month period, basically, where peak comes and goes. So if you do that calculation, some people might feel that we're not going to see the same winter surge that we just went through," Sethi said. "On the other hand, I am going to say there are still big unknowns, and what's happening nationally is not what's going to happen in every community where this is spreading."

(READ MORE: Latest COVID-19 surge among the deadliest for Chattanooga area)

Sethi said the goal should continue to be controlling the pandemic through vaccinations and other mitigation measures. The United States is expected to see another boost in new COVID-19 vaccine recipients once they're authorized for children age 5 and up, which is anticipated in the coming weeks.

"No doubt, when more people become eligible for vaccination, it'll help us control," he said. "I think that should be our goal — just simply to control this so our health care systems are not overwhelmed and people in general just don't feel so threatened by the prospect of severe COVID and death."

Contact Elizabeth Fite at or follow her on Twitter @ecfite.

Contact Wyatt Massey at or 423-757-6249. Follow him on Twitter @news4mass.