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Editor’s note: As more vaccinated people become sick with covid-19 some are wondering if the vaccinations work or work very well. The Minnesota Department of Health answers these and other questions in this report filed November 15, 2021.
COVID-19 vaccines are effective. However, some people who are fully vaccinated will still get COVID-19 if they are exposed to the virus that causes it. These are called “vaccine breakthrough cases.” We are tracking vaccine breakthrough cases in Minnesota and monitoring trends.
Vaccination can make illness less severe in people who get vaccinated but still get sick. Fully vaccinated people are also much less likely to be hospitalized or die than people with similar risk factors who are not vaccinated.
Background and case identification
COVID-19 vaccine breakthrough cases are identified by actively matching Minnesota case records with Minnesota vaccination records. MDH also takes and follows up on reports from health care providers, long term care, and correctional facilities. A vaccine breakthrough event could happen more than once for a person, but only the first instance of vaccine breakthrough will be counted in this data.
About COVID-19 vaccine breakthrough data
There are multiple points to consider when reviewing vaccine breakthrough data:
• As more people become vaccinated it is natural to see more cases of vaccine breakthrough (no vaccine is 100% effective). However, vaccines remain highly effective at preventing severe disease, hospitalization, and death.
• Vaccinated people should still take steps to protect themselves and others in certain settings such as indoor public settings and crowded outdoor areas.
• We may be seeing more vaccine breakthrough cases for many reasons including: • Waning immunity among people vaccinated earliest.
These people are also more likely to be older, have comorbidities, or work in a setting that puts them at higher risk for
COVID-19.
• The more-transmissible Delta variant may be playing a role that we don’t fully understand yet.
• 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.
• Vaccine breakthrough is not a measure of efficacy. There are several studies on vaccine effectiveness: CDC: COVID- 19 Vaccine Effectiveness Research.
Proportion of fully vaccinated cases, hospitalizations, and deaths
Vaccine breakthrough cases (VBT) represent the small portion of cases among people who belong to both the group of people who are COVID-19 cases and the group of people who are fully vaccinated. When we consider the proportion of COVID-19 cases that are VBT, we are not including any information about the larger populations of fully vaccinated or not fully vaccinated people in Minnesota.
• There are differences in the population of people who are fully vaccinated and the population of people who are not fully vaccinated. For example, the vaccinated population in Minnesota is older, more likely to have comorbidities, and more likely to work in high-risk settings.
• This means more people in the fully vaccinated population are at increased risk of developing, becoming hospitalized, or dying from COVID-19.
• Because the populations are different, you would have to make adjustments in order to directly compare them.
• For more information, please watch the “What Are Vaccine Breakthrough Cases” video.
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