A 23-year-old woman, who was accidentally administered six doses of the Pfizer BioNTech COVID-19 vaccine, has now been discharged from the hospital where she was being monitored for any adverse effect.

The vaccine was given at Noa hospital in Tuscany, central Italy, on Sunday, hospital spokeswoman Daniella Gianelli told CNN. The health worker, who administered the jab, mistakenly filled a syringe with an entire bottle, containing six doses.

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The patient, who is an intern in the hospital’s psychology department, was kept under strict observation and discharged on Monday. She was in “good health” with no underlying conditions, Gianelli said, adding that doctors will continue to monitor the patient’s immune response to “the massive dose of vaccine”.

An internal investigation has been opened, reported CNN quoting Gianelli, who added that it was “maybe just human error, definitively not on purpose.”

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According to the Italian government’s order, vaccination against COVID is mandatory for all healthcare and pharmacy workers, so that the medical staff, patients and vulnerable people can be protected.

The 23-year-old was supposed to get the vaccine before other people in her age group, as per the decree.