COVID-19: Illness After Vaccination

All children 6 months and older can now get a COVID-19 vaccine!

While we work to update our webpages with new information for kids ages 6 months through 4 years old, you can learn more about COVID-19 vaccines for children on the CDC website.

Jump to specific COVID-19 chart on this page:

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The COVID-19 vaccines are extremely effective at preventing serious illness, hospitalization, and death. Fully vaccinated people who test positive for COVID-19 more than 2 weeks after their completed vaccine dose series are called "breakthrough infections." No vaccine is 100 percent effective, and as such we expect to see some fully vaccinated people test positive for COVID-19. Breakthrough cases typically report mild illness or no symptoms.

Your likelihood of being infected with the virus that causes COVID-19 is determined by many factors, which include vaccinations, but also include the level of transmission and vaccine coverage in your community, whether you or others wear masks as recommended, the number of people you have close contact with, and more. On average, fully vaccinated individuals are less likely to be infected, hospitalized, and die from COVID-19 compared to unvaccinated individuals.

The Centers for Disease Control and Prevention (CDC) also monitors rates of COVID-19 cases and deaths by vaccination status and reports data from various jurisdictions, including Wisconsin. On the Rates of COVID-19 Cases by Vaccination Status and Booster Dose graph, you can see rates of COVID-19 cases and deaths among fully vaccinated people with and without an additional or booster dose and compare them to rates among unvaccinated people.

For the month of May 2022, the rate of confirmed and probable COVID-19 cases per 100,000 people by: 

  • Primary series only: 459.8
  • Primary series and booster: 1110.8
  • Unvaccinated: 1086.1

For the month of May 2022, the rate of COVID-19 hospitalizations per 100,000 people by:

  • Primary series only: 5.4
  • Primary series and booster: 10.7
  • Unvaccinated: 28.0

For the month of May 2022, the rate of COVID-19 deaths per 100,000 by:

  • Primary series only: 0.4
  • Primary series and booster: 1.1
  • Unvaccinated: 3.9

These rates are age-adjusted. Learn more about age-adjustment in the "Understanding our data" accordions below. 

 

DHS plans to update this data every month.This data is updated on a monthly basis, halfway through the following month, to account for the 2-week data lag in receiving COVID-19 reports and to ensure the most complete data is presented for the previous, full month.

 

Understanding our data: What does this chart mean?

This chart shows the age-adjusted rate of confirmed and probable cases, deaths, and hospitalizations per 100,000 amongst unvaccinated people, people who have completed only their primary COVID-19 vaccine series, and people who have received their primary series and booster by month. Viewing case, death, and hospitalization data as rates allows the three groups to be compared directly while accounting for differences in population size across groups, especially as the proportion of fully vaccinated and up to date people increases.

The above rates are age-adjusted. Age adjustment, or age standardization, is used in epidemiology to allow populations to be compared directly when the age distribution of who most commonly gets the disease, or seriously sick from the disease, is skewed. Almost all diseases or health outcomes occur at different rates in different age groups, and that is true of COVID-19. Older populations are, in general, more likely to experience severe illness and death due to COVID-19.

In the case of the COVID-19 vaccine, older populations were eligible to receive the vaccine before younger populations. As such, they represent a larger proportion of the fully vaccinated population. On the other hand, younger populations represent a larger proportion of the not fully vaccinated group. In order to more fairly compare rates of hospitalization and death among fully vaccinated and not fully vaccinated groups, we do an age adjustment so that the overall rates are based on the same population proportions. This is similar to calculating a rate per 100,000 in order to compare rates across populations of different sizes.

Please note: Data on whether or not a confirmed or probable case of COVID-19 is hospitalized is not always complete in WEDSS. As such, the true rate of hospitalization among the fully vaccinated and not fully vaccinated groups may differ slightly from what is presented here.

About our data: How do we measure this?

Data source: The Wisconsin Immunization Registry (WIR) and Wisconsin Electronic Disease Surveillance System (WEDSS).

Read our Frequently Asked Questions for more information on how cases of COVID-19 are reported in WEDSS.

Fully vaccinated people who test positive for COVID-19 more than 2 weeks after their completed vaccine dose series are called breakthrough infections. Breakthrough infections shown in the data only include those that meet the Centers for Disease Control (CDC) vaccine breakthrough infection definition. We identify vaccine breakthrough infections by comparing immunization records in WIR to confirmed and probable case records in WEDSS. This allows us to match person records between COVID-19 cases and vaccination status. 

  • The unvaccinated population includes individuals who have no COVID-19 vaccine doses reported in WIR.
  • The primary series only population includes individuals who have a complete primary COVID-19 vaccine series reported in WIR, which includes a single dose of the J&J COVID-19 vaccine or two doses of either the Pfizer or Moderna COVID-19 vaccine.
  • The primary series and booster population includes individuals who have a complete primary series and at least one additional or booster dose reported in WIR.

We plan to update our data monthly.

Back to a list of charts on this page.


Understanding our data: What does this chart mean?

This chart shows the crude rate of confirmed and probable cases, deaths, and hospitalizations per 100,000 amongst unvaccinated people, people who have completed only their primary COVID-19 vaccine series, and people who have received their primary series and booster by age group for the last month. The crude rate shows the rate based on the total number of incidences in that age group out of the total age group population multiplied by 100,000. The chart also displays the age-adjusted rates for the three groups to the right of the chart.

The above rates are age-adjusted. Age adjustment, or age standardization, is used in epidemiology to allow populations to be compared directly when the age distribution of who most commonly gets the disease, or seriously sick from the disease, is skewed. Almost all diseases or health outcomes occur at different rates in different age groups, and that is true of COVID-19. Older populations are, in general, more likely to experience severe illness and death due to COVID-19.

In the case of the COVID-19 vaccine, older populations were eligible to receive the vaccine before younger populations. As such, they represent a larger proportion of the fully vaccinated population. On the other hand, younger populations represent a larger proportion of the not fully vaccinated group. In order to more fairly compare rates of hospitalization and death among fully vaccinated and not fully vaccinated groups, we do an age adjustment so that the overall rates are based on the same population proportions. This is similar to calculating a rate per 100,000 in order to compare rates across populations of different sizes.

Viewing case, death, and hospitalization data as rates allows the two groups to be compared directly while accounting for differences in population size across groups, especially as the proportion of fully vaccinated people increases.

Please note: Data on whether or not a confirmed or probable case of COVID-19 is hospitalized is not always complete in WEDSS. As such, the true rate of hospitalization among the fully vaccinated and not fully vaccinated groups may differ slightly from what is presented here.

About our data: How do we measure this?

Data source: The Wisconsin Immunization Registry (WIR) and Wisconsin Electronic Disease Surveillance System (WEDSS).

Read our Frequently Asked Questions for more information on how cases of COVID-19 are reported in WEDSS.

Fully vaccinated people who test positive for COVID-19 more than 2 weeks after their completed vaccine dose series are called breakthrough infections. Breakthrough infections shown in the data only include those that meet the Centers for Disease Control (CDC) vaccine breakthrough infection definition. We identify vaccine breakthrough infections by comparing immunization records in WIR to confirmed and probable case records in WEDSS. This allows us to match person records between COVID-19 cases and vaccination status. 

  • The unvaccinated population includes individuals who have no COVID-19 vaccine doses reported in WIR.
  • The primary series only population includes individuals who have a complete primary COVID-19 vaccine series reported in WIR, which includes a single dose of the J&J COVID-19 vaccine or two doses of either the Pfizer or Moderna COVID-19 vaccine.
  • The primary series and booster population includes individuals who have a complete primary series and at least one additional or booster dose reported in WIR.

We plan to update our data monthly.

Back to a list of charts on this page.


Diagnosed with COVID-19?

If you have been diagnosed with COVID-19, isolate to prevent the spread of COVID-19.

 

 

An adult working in a test lab

 

Last Revised: June 23, 2022

How can I download DHS COVID-19 data?

All DHS COVID-19 data is available for download directly from the chart on the page. You can click on the chart and then click "Download" at the bottom of the chart (gray bar).

To download our data visit one of the following links:

Updated Data*

Data dictionary

*As of October 28, 2021, the data download links have been changed to reference daily summaries of the COVID-19 data. To access historical COVID-19 data, please reference the Open GIS Data website.

You can find more instructions on how to download COVID-19 data or access archived spatial data by visiting our FAQ page

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