How many total SARS-CoV-2 mRNA vaccine doses will the US FDA and CDC recommend for at least 15% of the US on December 31, 2024?

SARS-CoV-2 mRNA vaccines have been widely administered in the US during the COVID-19 pandemic. The two SARS-CoV-2 mRNA vaccines used in the US are the Pfizer-BioNTech and Moderna vaccines. As of June 5, 2022, the US has administered almost 570 million SARS-CoV-2 mRNA vaccine doses, which constitutes about 97% of the 588.5 million total SARS-CoV-2 vaccine doses administered.

As of June 2022, four doses (2 primary series, 2 booster doses) of each of the mRNA vaccines have been authorized by the US FDA and recommended by the US CDC for at least 15% of the US population.

The purpose of this question is to understand how frequently public health regulators and authorities will see the need to authorize/recommend additional SARS-CoV-2 mRNA doses over the next few years. This may indicate how valuable the development of a pan-sarbecovirus vaccine may be.