FDA in the United States authorized a Pfizer-BioNTech COVID‑19 booster dose for certain populations on September 22, 2021, with CDC advisory panel backing and CDC director sign‑off on September 23–24, 2021, after which booster shots began being administered nationally.

Sources:

• The FDA issued an Emergency Use Authorization (EUA) for a single Pfizer booster dose for high‑risk groups on Sept. 22, 2021.
• CDC’s ACIP recommended the booster on Sept. 23, 2021, and CDC’s director endorsed and slightly expanded those recommendations shortly thereafter, allowing boosters to begin for eligible groups in late September 2021.

Since boosters were both authorized and available in the U.S. market in September 2021, Friedberg’s prediction that “we’re going to get boosters and … see them hit the market next month in September” is correct for the United States and timeframe specified.