Messages about flu vaccines can get confusing, but advisories from health authorities remain clear: Almost everyone over six months of age should get a flu vaccine.
The dead include two civilians and a police officer from a local university. A suspect has been arrested, but no motive has been announced.
President Francois Hollande said France would continue to defend the values for which they died.
Demonstrators angry about the killing of a black teenager who was shot 16 times by a white police officer last year disrupted Black Friday shopping.