Vaccination is our best defense against COVID-19. Clinical trials and observational studies show that all COVID-19 vaccines authorized in the United States are effective at preventing COVID-19, especially severe disease, hospitalization, and death. Some vaccine breakthrough cases are expected, but getting the vaccine significantly reduces the chances of severe illness if an infection does occur.

The CDC recommends people 5 and older receive an age-appropriate, updated mRNA booster dose if at least 2 months have passed since their primary series or since their most recent booster dose. Updated boosters of Pfizer-BioNTech and Moderna contain a bivalent formula that both boosts immunity against the original coronavirus strain and also protects against the newer Omicron variants that cause most cases. Updated boosters are expected to provide better protection against the virus and address waning vaccine effectiveness over time.

Booster shots are not available for children under 5. See additional recommendations for people who are moderately to severely immunocompromised.