The FDA doesn't allow hand sanitizer brands to make claims about efficacy against contracting viruses, such as any stating that Purell hand sanitizers are effective against the flu. However, the agency noted that the Centers for Disease Control and Prevention recommends using alcohol-based hand sanitizer for flu prevention. Purell is made of ethyl alcohol.
Prevention is the key word here. Hand sanitzers are just that, a way to HELP prevent ourselves from get sick as often. In my opinion, they are a good option when you cannot find a good old fashioned sink and soap to properly wash your hands with. But still, nothing is guaranteed and we have to stop thinking that this gel in a bottle is a cure all for illness.