Last Updated: 11/10/2022
When reviewing vaccine breakthrough data, there are several important things to know:
- Vaccines are doing their job – they are highly effective preventing severe disease, hospitalization, and death.
- As more people become vaccinated it is natural to see more cases of vaccine breakthrough (no vaccine is 100% effective).
- We may be seeing more vaccine breakthrough cases for many reasons including:
- Waning immunity as more time passes from when people have received their most recent dose of COVID-19 vaccine.
- Variants that spread more easily may be playing a role.
- People are returning to various states of normalcy – this will result in varying levels of disease transmission and test seeking behaviors.
- Vaccination records may be incomplete as a result of reporting errors and delays or problems matching vaccination information with case data. In addition, some entities, including federal organizations, don't report vaccination information to the state.
- Breakthrough infection is not the same thing as breakthrough disease. Breakthrough infections occur any time a fully vaccinated person tests positive for COVID-19, regardless of whether they feel sick. This data report is on breakthrough infections, not breakthrough disease.
- Vaccine breakthrough data are not the same as vaccine effectiveness data. To determine vaccine's effectiveness, you need to be able to control for factors that may influence who becomes a COVID-19 case and who does not. We are not able to do that with vaccine breakthrough data. For more information on studies on vaccine effectiveness: CDC: COVID-19 Vaccine Effectiveness Research.
- At times, some breakthrough infection rates may appear equal or higher for people who are fully vaccinated. There are several reasons that this can happen, and some important things to keep in mind when interpreting the data:
- For shorter time periods, like the "last 60 days," when there are low case rates overall the data can be more significantly impacted by even a few cases. It does not mean the data are wrong or vaccine are not working. When you look at longer time periods or periods with higher case rates, you see the trend that vaccines are working to reduce hospitalizations and deaths.
- We are still learning about the relationship between new variants and vaccine breakthrough infection, especially for 5-11-year-olds since they were able to get vaccinated right when the Omicron variant surge started.
- There are differences between the vaccinated and unvaccinated populations, such as when they decide to get tested, which can make it more likely to find cases in certain groups. People with underlying health conditions who are at higher risk for a vaccinate breakthrough infection may be more likely to get vaccinated because of their health condition.
- For more information, please watch What Are Vaccine Breakthrough Cases.