West Ham Online

Does it stop you from getting the flu? If not what is the point of it? 

To be a complete pedant it covers you for the most common strains  - plural.
Gank is spot on for the rest.

It stops you getting the most common strain of flu of the time. Then the virus mutates and you need a new jab. Also you can still catch other, less widespread strains.

Uncle Gank sorts your problems