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A Project of The Annenberg Public Policy Center
SciCheck’s COVID-19/Vaccination Project

How effective are the vaccines?


This article is available in both English and Español

All of the authorized and approved vaccines are effective at preventing severe COVID-19.

Against earlier forms of the coronavirus, the vaccines were highly effective at preventing symptomatic illness. For example, clinical trials for the Pfizer/BioNTech and Moderna mRNA vaccines and the protein-based Novavax vaccine found each reduced the risk of getting sick by more than 90%.

Subsequent studies have demonstrated that the vaccines are effective under real-world conditions. Against omicron variants, however, the vaccines haven’t fared as well and are much worse at preventing infection or mild disease. The shots are still good at preventing hospitalization or death, though, particularly if someone stays up-to-date on vaccination.

Starting in September 2023, the Food and Drug Administration approved or authorized updated 2023-2024 vaccines that target the latest prevalent omicron variants. The Centers for Disease Control and Prevention recommends these vaccines for everyone 6 months or older. For more on these shots, see our “Q&A on the Updated COVID-19 Vaccines.”