Dreonna Breton worked as a registered nurse for Horizons Healthcare Services in central Pennsylvania. The company requires all personnel to get the influenza vaccine.
Breton contends the immunizations may not be safe enough for pregnant women. She suffered two miscarriages earlier this year, and doesn't want to risk a third.
Company spokesman Alan Peterson says it's unconscionable for a health care worker not to be immunized. He also says pregnant women are more susceptible to the flu.
Breton offered to wear a mask during flu season. But the 29-year-old was fired Dec. 17.
Federal officials say the flu causes about 200,000 hospitalizations annually.