Final answer:
The U.S. Food and Drug Administration (FDA) provided emergency use authorization to Pfizer's COVID-19 vaccine prior to acceptance by the CDC.
Step-by-step explanation:
The agency of the U.S. government that gave emergency use authorization to Pfizer's coronavirus vaccine before it was accepted by the CDC is the Food and Drug Administration (FDA).
This authorization process allowed for the use of the vaccine during the public health crisis even though it had not yet gone through the entire formal approval process that vaccines typically undergo before they are widely distributed. The decision was made given the urgency of the COVID-19 pandemic and the need to take swift action to start immunizing the public against the virus.