COVID-19 Outcomes by Vaccination Status

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COVID-19 Case Rates in Chicago: Vaccinated vs Unvaccinated

COVID-19 Outcomes by Vaccination Status

This historical dataset shows the weekly rates of COVID-19 cases among Chicago residents, broken down by vaccination status.

Time frame: “Fully vaccinated” and “Unvaccinated” data begin the week ending April 3, 2021. “Boosted” data begin the week ending October 23, 2021.

Outcomes: Cases: positive PCR or antigen test (reported in I-NEDSS). Reinfections may be counted more than once.

Vaccination status: Unvaccinated: no doses prior to positive test. Fully vaccinated: primary series completed ≥14 days before a positive test (no other positives in prior 45 days). Boosted: fully vaccinated + booster dose ≥14 days before positive test. Partially vaccinated individuals are excluded.

Rate calculation: (Weekly events ÷ group population) × 100 000. Incidence rate ratios (IRRs) compare unvaccinated vs. each vaccinated group.

Notes: Provisional data, updated weekly. Counts by week of test. Population totals from the 2019 American Community Survey.

Detailed Explanation of the Charts

The HTML file (vaccinated_vs_unvaccinated_covid_charts.html) contains two bar charts visualizing COVID-19 case rates in Chicago, comparing unvaccinated and fully vaccinated individuals.

Chart 1: COVID-19 Case Rates (All Ages) Purpose: This bar chart compares COVID-19 case rates per 100,000 people for unvaccinated vs. fully vaccinated individuals across three time periods: May 2021 (Delta variant), January 2022 (Omicron variant), and July 2023 (post-Omicron). Data Description: X-Axis: Three periods: May 29, 2021 (Delta), January 1, 2022 (Omicron), July 1, 2023 (post-Omicron). Y-Axis: Case rates per 100,000 people, starting at zero. Datasets: Unvaccinated: Rates of 639 (May 2021), 25,475 (January 2022, 12-17 age group), and 105 (July 2023). Fully Vaccinated: Rates of 68 (May 2021), 18,274 (January 2022, 12-17 age group), and 55 (July 2023). Visual Elements: Unvaccinated rates in red (rgba(255, 99, 132, 0.6)). Vaccinated rates in blue (rgba(54, 162, 235, 0.6)). Bars grouped by period. Key Insights: May 2021: Unvaccinated rate 9.4 times higher (639 vs. 68). January 2022: Both rates high, unvaccinated 1.4 times higher (25,475 vs. 18,274). July 2023: Low rates, unvaccinated 1.9 times higher (105 vs. 55).

Chart 2: COVID-19 Case Rates (Age 65-79) Purpose: Compares case rates for unvaccinated vs. fully vaccinated individuals in the 65-79 age group. Data Description: X-Axis: Periods: May 29, 2021 (using October 9, 2021 data), January 22, 2022, March 4, 2023. Y-Axis: Case rates per 100,000 people. Datasets: Unvaccinated: Rates of 927 (May 2021), 5,824 (January 2022), 1,274 (March 2023). Fully Vaccinated: Rates of 413 (May 2021), 4,166 (January 2022), 1,083 (March 2023). Visual Elements: Same as Chart 1. Key Insights: May 2021: Unvaccinated rate 2.2 times higher (927 vs. 413). January 2022: Unvaccinated rate 1.4 times higher (5,824 vs. 4,166). March 2023: Unvaccinated rate 1.2 times higher (1,274 vs. 1,083).

Explanation of the Data Table

The dataset contains 1,000 entries of weekly COVID-19 case rates in Chicago by vaccination status and age group, from April 2021 to December 2023.

Structure: Columns: outcome, week_end, age_group, unvaccinated_rate, vaccinated_rate, boosted_rate, crude_vaccinated_ratio, population_unvaccinated, population_vaccinated, population_boosted, outcome_unvaccinated, outcome_vaccinated, outcome_boosted, age_group_min, age_group_max. Time Frame: Unvaccinated and vaccinated data from April 3, 2021; boosted from October 23, 2021. Definitions: Unvaccinated: No doses before positive test. Fully Vaccinated: Primary series ≥14 days before positive test, no prior positives in 45 days. Boosted: Fully vaccinated + booster ≥14 days before positive test. Rate Calculation: (Weekly cases ÷ population) × 100,000. Notes: Provisional data, 2019 ACS population estimates.

Data Used: Chart 1: May 29, 2021 (All: 639 vs. 68), January 1, 2022 (12-17: 25,475 vs. 18,274), July 1, 2023 (All: 105 vs. 55). Chart 2: October 9, 2021 (65-79: 927 vs. 413), January 22, 2022 (65-79: 5,824 vs. 4,166), March 4, 2023 (65-79: 1,274 vs. 1,083).

Significance: Shows higher unvaccinated case rates, especially during Delta. Gap narrows with Omicron and later variants. Vaccines reduced case rates, particularly for 65-79 age group.

Limitations: Only case data provided. Incomplete “All” age group data for some weeks. Provisional data subject to revisions.

Sources and Web Addresses: Chicago Department of Public Health: Title: “COVID-19 Outcomes by Vaccination Status” Web Address: [data.cityofchicago.org] Chart.js: Version: 4.4.0 Web Address: https://www.chartjs.org/ CDN: https://cdn.jsdelivr.net/npm/chart.js@4.4.0/dist/chart.umd.min.js