Half of those affected were cancer patients already weakened by chemotherapy treatment that left them less able to fight off the deadly bacteria, the Health Protection Agency found.
At least 20 others were also poisoned by listeria but survived.
Sandwiches were found to account for almost three quarters of outbreaks in hospitals.
The bacteria was also found in ham salad, sliced sausage, tuna, cheese and prawn mayo.
Almost all the food were pre-packed by commercial firms, but at some stage had not been kept below five degrees Celsius, the report said.
The agency said the report suggests "catering and ward staff are not aware of the importance of temperature control, or that proper methods of refrigeration were not used".
Source: IANS
