As Cara succinctly put it in Saturday's Good Morning, News!, "don't inadvertently cause the death an old person or a kid."
Or, per the New Yorker:
...Even if you think you are invincible, your elderly neighbors and infant children are not. People with weakened immune systems-those undergoing cancer treatments, for example-are not. Your parents and grandparents are not. The flu vaccine is not perfect, but it's what we have. It's available at drug-store chains and malls, big-box superstores and, naturally, at your doctor's office. Get one today.
Plug your zip code into this site, and it'll tell you where to find a vaccine. Call first, 'cause Portland pharmacies and clinics are running low.