Multiple data points show that by late April and into May 2021 U.S. vaccine supply was exceeding the short‑term public demand for shots.

• On April 23, 2021, an AP report described how "the supply of coronavirus vaccine doses in the U.S. outpaces demand," with states like Louisiana, Kansas, and Mississippi turning down all or part of their federal allocations because they could not use them. (medicalxpress.com)

• A May 8, 2021 report detailed that several states (e.g., Iowa, Kansas, Illinois, Connecticut, South Carolina) requested only a fraction of their available allotments, explicitly citing softening demand and significant inventories already on hand; New York City was seeing daily shots down about 40% from a mid‑April peak. (dailysceptic.org)

• CDC data show U.S. daily vaccinations peaked in mid‑April 2021 (~3.3 million per day) and then declined sharply afterward, despite continued strong manufacturing and distribution, indicating that demand—not supply—became the binding constraint. (en.wikipedia.org)

• Policy and think‑tank analyses from March–June 2021 discussed the U.S. as having secured and soon to have a surplus of doses relative to the number of Americans willing to be vaccinated, anticipating large excess stocks by mid‑2021 and beyond. (washingtonpost.com)

Taken together, these sources show that by (and even slightly before) May 2021, available U.S. COVID‑19 vaccine doses exceeded near‑term public demand, matching Friedberg’s prediction of an oversupply relative to demand.