Allocations of Johnson & Johnson's coronavirus vaccine will plummet by 80% next week, according to data released by the Centers for Disease and Control Prevention.

Why it matters: J&J's single-dose shot is viewed as key to U.S. efforts to vaccinate enough Americans to reach herd immunity as soon as possible. A spokesperson told the Wall Street Journal that J&J is still aiming to meet its goal of delivering 100 million doses by June.

By the numbers: 4.9 million J&J doses were allocated to states, territories and federal agencies this week. Next week, that number will plunge to 700,000, according to the CDC.

• It's unclear what caused the sharp decline, but federal officials have warned that supply will fluctuate week to week, according to the WSJ.
• The week of March 1 saw 2.8 million doses distributed, while the following two weeks' supply fell to around 400,000 to 500,000 doses per week.

The big picture: Manufacturing challenges have plagued J&J from the start, heightening concerns that the company won't be able to meet its goals of 100 million U.S. doses by mid-year and up to 1 billion by the end of 2021.

• Some states are already rewriting their distribution plan ahead of next week's decrease in supply. Several have publicly committed to reopening by a certain date.
• A plant in Baltimore recently ruined 15 million J&J vaccines, though the incident was not expected to affect deliveries nationwide.
• J&J declined to comment on next week's supply to the WSJ.