MADISON, Wisc. — U.S. states asked the federal government this week to withhold staggering amounts of COVID-19 vaccine amid plummeting demand for the shots, contributing to a growing U.S. stockpile of doses.

From South Carolina to Washington, states are requesting the Biden administration send them only a fraction of what’s been allocated to them. The turned-down vaccines amount to hundreds of thousands of doses this week alone, providing a stark illustration of the problem of vaccine hesitancy in the U.S.

More than 150 million Americans — about 57% of the adult population — have received at least one dose of vaccine, but government leaders are doing everything they can to persuade the rest of the country to get inoculated.

The Biden administration announced this week that if states don’t order all the vaccine they’ve been allotted, the administration will shift the surplus to meet demand in other states.