Effectiveness of the COVID-19 vaccine | COVID-19

Dataset location and more detailed description: https://data.cityofchicago.org/Health-Human-Services/COVID-19-Outcomes-by-Vaccination-Status/6irb-gasv

Rates for fully vaccinated and unvaccinated people begin the week ending April 3, 2021, when COVID-19 vaccines became widely available in Chicago. Recall rates begin the week ending October 23, 2021 after recalls were recommended by the Centers for Disease Control and Prevention (CDC) for adults 65 and older and adults in certain populations and occupational and high-risk institutional individuals who received Pfizer or Moderna for their primary series or anyone who received the Johnson & Johnson vaccine.

Vaccination status:

  • Fully Vaccinated: Completion of the primary series of a COVID-19 vaccine cleared or approved by the United States Food and Drug Administration (FDA) at least 14 days prior to a positive test (with no further positive tests within 45 days previous ones).
  • Boosted: Fully vaccinated with an additional or booster dose of any licensed or FDA-approved COVID-19 vaccine received at least 14 days prior to a positive test (with no other positive tests in the previous 45 days).
  • Unvaccinated: No evidence of having received a dose of an FDA cleared or approved vaccine prior to a positive test.
  • CLARIFICATION NOTE: Those who started but did not complete all recommended doses of an FDA cleared or approved vaccine before testing positive (i.e. partially vaccinated) are excluded from this visual.

Results :

  • Cases: Individuals with a positive molecular test (PCR) or COVID-19 antigen result from an FDA-cleared COVID-19 test that has been reported in the I-NEDSS. A person may be re-infected with SARS-CoV-2 over time and therefore may be counted more than once in this data set. Cases are counted by week the test sample was collected.
  • Hospitalizations: Cases of COVID-19 who are hospitalized with documented illness related to COVID-19 or who are admitted for any reason within 14 days of a positive SARS-CoV-2 test. Hospitalizations are counted per week of hospitalization.
  • Deaths: COVID-19 cases who died from health complications related to COVID-19, as determined by vital records or a public health investigation. Deaths are counted by week of death.

Hospitalization data is off by one week. Death data is delayed for two weeks.

Incidence rates for fully vaccinated but unboosted people are calculated as the total fully vaccinated but unboosted with the result divided by the total number of fully vaccinated but unboosted people at the end of each week. The boosted incidence rates are calculated as the total boosted with the result divided by the cumulative boosted at the end of each week. Incidence rates for the unvaccinated are calculated as the total unvaccinated with the result divided by the total population minus the cumulative number of vaccinated, fully and partially vaccinated at the end of each week. All rates are multiplied by 100,000.

Overall age- and IRR-adjusted incidence rates are standardized using the 2000 US Census standard population. Rates by age group are crude rates.

Incidence rate ratios (IRR) for the last eight weeks were calculated by dividing the cumulative unvaccinated rate by the cumulative vaccinated rate and by the cumulative recall rate.

All data is provisional and subject to change. Information is updated as more details are received and it is, in fact, very common for recent dates to be incomplete and updated over time. This dataset reflects data known to CDPH at the time the dataset is updated weekly.

Numbers in this dataset may differ from those in other public sources due to when the data is reported and how the Chicago city limits are defined.

Sara H. Byrd