The U.S. Centers for Disease Control and Prevention expects COVID-19 vaccine boosters targeting circulating variants of the virus to be available for children aged 5-11 years by mid-October.

The CDC said in a document released on Tuesday that it expects to make a recommendation in early- to mid-October on the use of the new bivalent vaccines in the group, if they are authorized by the U.S. Food and Drug Administration (FDA).

The vaccines, which target both the original version and the currently circulating variants of the virus, were rolled out for people 12 years or older earlier this month.

The CDC said it expects Pfizer-BioNTech's (PFE.N), bivalent vaccine to be available for children aged 5-11 years, and Moderna's (MRNA.O) vaccine for those aged 6-17 years, pending FDA authorization.

The Pfizer vaccine is already authorized as a booster dose for children over 12 years of age, while Moderna's bivalent vaccine is authorized for adults.

The CDC expects pre-orders for the Pfizer shot to begin for the age group next week. The Moderna vaccine will have the same formulation for children and adults and will not require a separate pre-order period, the CDC said.

The United States government has ordered more than 170 million updated vaccine booster shots for this fall, and said on Tuesday it had sent out over 25 million doses.