In this March 2, 2021, file photo, pharmacy technician Hollie Maloney loads a syringe with Pfizer's COVID-19 vaccine at the Portland Expo in Portland, Maine. The U.S. gave full approval to Pfizer's COVID-19 vaccine on Monday, Aug. 23, 2021. Credit: Robert F. Bukaty / AP

Maine’s Cumberland County is among the U.S. counties with the highest COVID-19 vaccination rates, a factor that likely helped its case numbers stay lower than the rest of the state during a delta variant surge in the last month.

Out of more than 3,000 counties where the U.S. Centers for Disease Control and Prevention tracks data, Cumberland County ranks 19th, with 86.2 percent of its eligible population aged 12 and older fully vaccinated. Among counties with a population of at least 200,000, it ranks fifth, trailing only two counties in the greater San Francisco Bay area in California and two counties in Maryland outside of Washington, D.C.

Several other Maine counties also rank highly. Knox and Lincoln counties rank 28th and 48th respectively, while York County ranks 56th overall and 23rd among counties with at least 200,000 people. Four Maine counties are still yet to reach two-thirds of the eligible population vaccinated, which would bring them in line with the national average.

Both state and national data continue to reflect a strong correlation between local vaccination rates and overall COVID-19 case rates as the highly contagious delta variant poses the most risk for unvaccinated people. Since Sept. 1, Cumberland County’s COVID-19 case rate is more than 40 percent lower than Maine’s overall rate. Maine’s least vaccinated county, Somerset, has seen a case rate more than three times higher than Cumberland during that period.

Maine’s most populous county, which saw higher case rates than much of the state when the virus first arrived in Maine and again last winter before vaccines were widely available, has also seen a lower death rate over the last few months as it exhibits a higher vaccination rate among its older population than the rest of Maine.

Just shy of 99 percent of Cumberland County residents aged 60 and older are fully vaccinated, according to state data, compared to 90 percent of overall Mainers in that age group.