Italy’s drug regulator, the Italian Pharmaceutical Agency (AIFA), said in a statement on Sunday that it was investigating an additional ten cases, on top of three reported late last week.
The most recent fatality was an 83-year-old from Umbria, the agency said.
The agency last week banned the use of two batches of the Fluad vaccine after three people died within 48 hours of receiving it.
Out of the other 12 cases, two each were in Sicily, Puglia, Tuscany, Emilia Romagna and Lombardy, while there was one each in Molise and Lazio.
AIFA said that a detailed investigation by the Pharmacovigilance Risk Assessment Committee at the European Medicines Agency would get underway on Monday and was expected to be completed by Thursday.
Basel-based Novartis said in a statement last week that it had been notified by AIFA "of the precautionary suspension of two lots of Fluad in Italy following reports of the serious adverse effects events after vaccination" and that “no causal relationship to the vaccine has been established."
A review of the two batches "has confirmed that they are in conformity with all production and quality standards," the company added.
The suspected batches were produced at a Novartis plant in the Tuscan city of Siena.
Novartis said Fluad had been used since 1997, during which time over 65 million doses have been successfully administered throughout the world, "which confirms the data gathered during clinical studies which involved over 70,000 patients."