Oseltamivir
"My wife and son both got the H3N2 strain that wasn't covered by the vaccine and I hadn't had the flu in about 20 years, so there was no chance I had any immunity.  I asked my doc for a prophylaxis prescription of Tamiflu, and being the cool doc that he is, he obliged.  In spite of being coughed on  multiple times by my son and caring for 2 people who had the flu, I remained flu free.  I'm very impressed.  I'm amazed people have to pull teeth the get a prescription for this medicine as a prophylaxis."