Sonia Acevedo, 41, suffered a 'sudden death' at home on New Year's Day 48 hours after receiving the jab. An autopsy is expected to take place later today or tomorrow.
The mother-of-two, who worked in paediatrics at the Portuguese Institute of Oncology in Porto, is not said to have suffered any adverse side-effects after being vaccinated.
Ms Acevedo's father Abilio Acevedo told Portuguese daily Correio da Manha: 'She was okay. She hadn't had any health problems.