At the end of March, CDC estimated that the BA.2 Omicron variant was the dominant COVID-19 strain in the United States. BA.2 is a subvariant of Omicron and has some key genetic differences from the original Omicron variant, B.1.1.529, that may make it more infectious. Current 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.

Scientists are still learning how effective COVID-19 vaccines are at preventing infection from Omicron and its subvariants. Current vaccines are expected to protect against severe illness, hospitalizations, and deaths due to infection with Omicron. However, breakthrough infections in people who are vaccinated are likely to occur. 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.

See additional recommendations for people who are moderately to severely immunocompromised. A second booster dose is recommended for certain people at increased risk of severe disease.