Monitoring COVID-19 Cases, Hospitalizations, and Deaths by Vaccination Status
COVID-19 Infection after Vaccination
COVID-19 vaccines help protect against severe illness, hospitalization, and death. People who are up to date on COVID-19 vaccines are much less likely to experience severe symptoms than people who are not up to date, if they get infected with SARS-CoV-2, the virus that causes COVID-19.
People who get infected after vaccination can spread COVID-19 to other people. When more virus is circulating, more infections will occur even where vaccination rates are high. If you live in a county with a high COVID-19 Community Level, you and others in your community, whether vaccinated or not, should take more steps to protect yourself and others, such as increasing indoor ventilation or wearing a mask in indoor public places.
Monitoring COVID-19 Rates by Vaccination Status
CDC uses public health surveillance data reported by participating health departments, hospitals, and long-term care facilities to monitor rates of COVID-19 cases, hospitalizations, and deaths by vaccination status.
Monitoring rates of COVID-19 cases, hospitalizations, and deaths by vaccination status over time, as well as by age, can help identify overall patterns or trends.
CDC analyzes surveillance data by vaccination status to
- Better understand patterns of COVID-19 among people who are vaccinated and unvaccinated.
- Identify signals of potential changes in vaccine effectiveness, which can be confirmed through more robust, controlled vaccine effectiveness studies.
CDC uses the following platforms and methods to collect and analyze surveillance data on COVID-19 cases, hospitalizations, and deaths by vaccination status:
CDC collaborates with many state and local health departments that regularly link case surveillance, immunization registry, and vital registration data to monitor rates of COVID-19 cases and deaths by vaccination status, including receipt of booster doses. These rates are published monthly on COVID Data Tracker.
Data from the participating health departments represent a large proportion of the U.S. population and all regions of the country. The volume of this data allows CDC to analyze important outcomes, like COVID-19-associated deaths. However, while these analyses may provide signals of potential changes in vaccine effectiveness, they cannot account for some factors that could impact the results – for example, underlying medical conditions or prior infection.
Analyses of these case surveillance data by vaccination status were published in CDC’s MMWR for periods of the Delta variant and Omicron variant.
CDC monitors rates of COVID-19 hospitalizations by vaccination status using COVID-NET. COVID-NET is a population-based, sentinel surveillance system that collects reports of laboratory-confirmed COVID-19-associated hospitalizations. COVID-NET covers approximately 10% of the U.S. population.
CDC publishes monthly rates of laboratory-confirmed COVID-19 hospitalizations by vaccination status on COVID Data Tracker. The data is updated monthly.
National Healthcare Safety Network
Infections in long-term care facility residents by vaccination status are reported through a network of approximately 15,000 medical facilities called the National Healthcare Safety Network (NHSN). Analyses of these long-term care facility data were published in CDC’s MMWR:
- Effectiveness of Pfizer-BioNTech and Moderna Vaccines in Preventing SARS-CoV-2 Infection
- Effectiveness of a COVID-19 Additional Primary or Booster Vaccine Dose in Preventing SARS-CoV-2 Infection
In addition, NHSN is used to monitor weekly infections by vaccination in dialysis patients among approximately 8,000 dialysis facilities.