What to know
Vaccine effectiveness is a measure of how well vaccination works under real-world conditions to protect people against health outcomes such as infection, symptomatic illness, hospitalization, and death.
What ÐÇ¿ÕÓéÀÖ¹ÙÍø is doing
Results of vaccine effectiveness studies are critical to ÐÇ¿ÕÓéÀÖ¹ÙÍø’s vaccine program and national vaccine policy decision-making.
The overall goal of ÐÇ¿ÕÓéÀÖ¹ÙÍø’s vaccine effectiveness program is to generate the comprehensive evidence needed to inform COVID-19 vaccine policy decisions and ÐÇ¿ÕÓéÀÖ¹ÙÍø guidance on other prevention measures.
To accomplish this, ÐÇ¿ÕÓéÀÖ¹ÙÍø in collaboration with public health and academic partners, conducts observational studies to evaluate the real-world effectiveness of authorized and licensed COVID-19 vaccines in the United States.
These studies generate data on how well vaccines work according to:
- Age group (for example, young children, adolescents, adults, and adults ages 65 and older)
- Risk group (for example, people with underlying health conditions and pregnant women)
- Risk setting (for example, residents of long-term care facilities and healthcare workers)
- Outcome (for example, against severe outcomes, such as hospitalization or death; and milder outcomes, such as symptomatic infection)
- Vaccine product (for example, original monovalent, bivalent, or updated [2023-24] monovalent)
- Vaccine dose (for example, primary series, additional doses, time since last dose)
ÐÇ¿ÕÓéÀÖ¹ÙÍø is committed to routinely evaluating vaccine effectiveness to detect changes that could be due to:
- Emerging SARS-CoV-2 variants
- Waning of vaccine protection
This work helps ÐÇ¿ÕÓéÀÖ¹ÙÍø identify population subgroups who may benefit from additional doses in the future.
Updates summarizing the results of ÐÇ¿ÕÓéÀÖ¹ÙÍø led vaccine effectiveness evaluations are provided on .
Guiding principles for monitoring vaccine effectiveness
The goals of ÐÇ¿ÕÓéÀÖ¹ÙÍø’s COVID-19 vaccine effectiveness program are to evaluate existing COVID-19 vaccines and inform decisions by the U.S. Advisory Committee on Immunization Practices regarding COVID-19 vaccine policy. ÐÇ¿ÕÓéÀÖ¹ÙÍø accomplishes these goals by:
- Assessing COVID-19 vaccine effectiveness in key populations and against key outcomes (see below)
- Providing timely data to evaluate effectiveness of new vaccine recommendations
- Detecting changes in COVID-19 vaccine effectiveness due to waning of vaccine-induced protection and emergence of new variants
- Including populations at high risk for severe COVID-19
- Communicating findings to policy makers, the scientific community, the public, and other stakeholders