The virus that causes COVID-19 is constantly changing, and new variants of the virus are expected to occur. The Omicron variant spreads more easily than the original virus and can infect people who have been vaccinated or have previously had COVID-19. Omicron has multiple sub lineages that are classified as variants of concern. CDC publishes information about the proportion of variants in the U.S. every week on its website.
COVID-19 vaccines remain the best public health measure to protect people from COVID-19 and reduce the likelihood of new variants emerging. This includes primary series, booster shots and additional doses for those who need them.
Pfizer-BioNTech and Moderna have each created an updated booster dose formula designed to protect against original strains of the virus, as well as Omicron variants that cause most new infections. The CDC recommends people 6 months 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.For children age 6 months to 4 years who get the Pfizer primary series, the updated bivalent vaccine will be used as the third dose in the series, rather than as a separate booster.
People who are up to date with their COVID-19 vaccines and get COVID-19 are less likely to develop serious illness than those who are unvaccinated and get COVID-19.