Americans are expected to have more options to protect themselves against COVID-19 in the fall.
The vaccines would target the omicron variant. According to the Centers for Disease Control and Prevention, the omicron subvariant BA.5 makes up about 80% of new COVID-19 cases in the country.
Health officials say the subvariant is highly contagious, but no more likely to cause severe outcomes.
Pfizer and Moderna have developed the updated vaccines, which are still going through the regulatory process.
The Department of Health and Human Services (HHS) announced an agreement to purchase 66 million booster doses ahead of their anticipated authorization.
HHS said the purchase is in addition to 105 million updated vaccines acquired from Pfizer.
The vaccines will eventually be shipped to states and offered at no cost.