SIOUX CITY, Iowa (Stacker) — The vaccine deployment in December 2020 signaled a turning point in the COVID-19 pandemic. By the end of May 2021, 40% of the U.S. population was fully vaccinated. But as vaccination rates lagged over the summer, new surges of COVID-19 came, including Delta in the summer of 2021, and now the Omicron variant, which comprises the majority of cases in the U.S.

Researchers around the world have reported that Omicron is more transmissible than Delta, making breakthrough and repeat infections more likely. Early research suggests this strain may cause less severe illness than Delta and the original virus, however, health officials have warned an Omicron-driven surge could still increase hospitalization and death rates—especially in areas with less vaccinated populations.

The United States as of Jan. 25 reached 870,916 COVID-19-related deaths and 72 million COVID-19 cases, according to Johns Hopkins University. Currently, 63.4% of the population is fully vaccinated, and 40.1% have received booster doses.

Stacker compiled a list of the counties with the highest COVID-19 infection rates in Iowa using data from the U.S. Department of Health & Human Services and vaccination data from Covid Act Now. Counties are ranked by the highest infection rate per 100,000 residents within the week leading up to Jan. 24, 2021. Cumulative cases per 100,000 served as a tiebreaker.

#40. Plymouth County, IA

– New cases per 100k in the past week: 1,096 (276 new cases, +19% change from previous week)
– Cumulative cases per 100k: 22,942 (5,776 total cases)
— 6.1% more cases per 100k residents than Iowa
– Cumulative deaths per 100k: 369 (93 total deaths)
— 39.8% more deaths per 100k residents than Iowa
– Population that is fully vaccinated: 51.1% (12,876 fully vaccinated)
— 15.0% lower vaccination rate than Iowa

#36. Calhoun County, IA

– New cases per 100k in the past week: 1,138 (110 new cases, +31% change from previous week)
– Cumulative cases per 100k: 24,173 (2,337 total cases)
— 11.8% more cases per 100k residents than Iowa
– Cumulative deaths per 100k: 207 (20 total deaths)
— 21.6% less deaths per 100k residents than Iowa
– Population that is fully vaccinated: 57.7% (5,583 fully vaccinated)
— 4.0% lower vaccination rate than Iowa

#35. Osceola County, IA

– New cases per 100k in the past week: 1,141 (68 new cases, +6% change from previous week)
– Cumulative cases per 100k: 21,417 (1,276 total cases)
— 1.0% less cases per 100k residents than Iowa
– Cumulative deaths per 100k: 336 (20 total deaths)
— 27.3% more deaths per 100k residents than Iowa
– Population that is fully vaccinated: 44.1% (2,630 fully vaccinated)
— 26.6% lower vaccination rate than Iowa

#33. Lyon County, IA

– New cases per 100k in the past week: 1,148 (135 new cases, +14% change from previous week)
– Cumulative cases per 100k: 21,625 (2,542 total cases)
— 0.0% less cases per 100k residents than Iowa
– Cumulative deaths per 100k: 383 (45 total deaths)
— 45.1% more deaths per 100k residents than Iowa
– Population that is fully vaccinated: 40.0% (4,707 fully vaccinated)
— 33.4% lower vaccination rate than Iowa

#20. Sac County, IA

– New cases per 100k in the past week: 1,276 (124 new cases, +49% change from previous week)
– Cumulative cases per 100k: 21,757 (2,115 total cases)
— 0.6% more cases per 100k residents than Iowa
– Cumulative deaths per 100k: 288 (28 total deaths)
— 9.1% more deaths per 100k residents than Iowa
– Population that is fully vaccinated: 51.5% (5,004 fully vaccinated)
— 14.3% lower vaccination rate than Iowa

#16. Clay County, IA

– New cases per 100k in the past week: 1,299 (208 new cases, +26% change from previous week)
– Cumulative cases per 100k: 22,240 (3,562 total cases)
— 2.8% more cases per 100k residents than Iowa
– Cumulative deaths per 100k: 250 (40 total deaths)
— 5.3% less deaths per 100k residents than Iowa
– Population that is fully vaccinated: 50.7% (8,125 fully vaccinated)
— 15.6% lower vaccination rate than Iowa

#14. Cherokee County, IA

– New cases per 100k in the past week: 1,308 (147 new cases, +37% change from previous week)
– Cumulative cases per 100k: 23,427 (2,632 total cases)
— 8.3% more cases per 100k residents than Iowa
– Cumulative deaths per 100k: 481 (54 total deaths)
— 82.2% more deaths per 100k residents than Iowa
– Population that is fully vaccinated: 51.6% (5,801 fully vaccinated)
— 14.1% lower vaccination rate than Iowa

#12. O’Brien County, IA

– New cases per 100k in the past week: 1,323 (182 new cases, +38% change from previous week)
– Cumulative cases per 100k: 22,170 (3,049 total cases)
— 2.5% more cases per 100k residents than Iowa
– Cumulative deaths per 100k: 487 (67 total deaths)
— 84.5% more deaths per 100k residents than Iowa
– Population that is fully vaccinated: 49.3% (6,786 fully vaccinated)
— 18.0% lower vaccination rate than Iowa

#2. Buena Vista County, IA

– New cases per 100k in the past week: 1,672 (328 new cases, +71% change from previous week)
– Cumulative cases per 100k: 29,235 (5,736 total cases)
— 35.2% more cases per 100k residents than Iowa
– Cumulative deaths per 100k: 260 (51 total deaths)
— 1.5% less deaths per 100k residents than Iowa
– Population that is fully vaccinated: 65.4% (12,840 fully vaccinated)
— 8.8% higher vaccination rate than Iowa

#1. Woodbury County, IA

– New cases per 100k in the past week: 1,788 (1,844 new cases, +17% change from previous week)
– Cumulative cases per 100k: 24,823 (25,594 total cases)
— 14.8% more cases per 100k residents than Iowa
– Cumulative deaths per 100k: 285 (294 total deaths)
— 8.0% more deaths per 100k residents than Iowa
– Population that is fully vaccinated: 54.4% (56,058 fully vaccinated)
— 9.5% lower vaccination rate than Iowa

For the list of all 50 counties with highest COVID-19 infection rates in Iowa, click here.