A 23-year-old Italian woman was mistakenly given six doses of the Pfizer BioNTech Covid-19 vaccine. The woman was given the vaccine at the Noa hospital in Tuscany, central Italy, on Sunday. Fortunately, she did not suffer any adverse side effects after receiving the over-dose.

The woman was kept under observation for 24 hours for any adverse reaction and was discharged on Monday.

The patient is in "good health" with no underlying conditions.

A health worker accidentally filled a syringe with an entire bottle of the vaccine, which contained six doses. She realised her mistake only after the shot was administered to the woman.

"She saw five empty syringes and realized her mistake," hospital spokeswoman Daniella Gianelli told CNN.

Doctors will continue to monitor the response of the woman's immune to the "massive dose of vaccine".

The woman was given the vaccine before other people in her age group as she is an intern in the hospital's psychology department.

Gianelli said that an internal investigation is underway and added that it was "maybe just human error, definitively not on purpose."

The Italian government passed a decree in April making it mandatory for all healthcare and pharmacy workers to get vaccinated to protect medical staff, patients and vulnerable people.

Healthcare workers who refuse to get vaccinated will be given, wherever possible, roles in which there is no contact with Covid patients. In cases where there is no option, healthcare workers will be suspended without pay.

Overdoses of the Pfizer vaccine have earlier been reported in the United States, Australia, Germany and Israel.