Last Monday, Meredith and I both decided to get the flu vaccine that was being offered through my work. I felt fine (other than waking up Tuesday morning with a very sore arm that lasted for a couple of days), but Meredith has had the 'flu-like symptoms' that they mention as a possible side effect since Monday evening.
At some point, the line between flu and 'flu-like symptoms that aren't really the flu' gets pretty blurry. If you have a slight fever, are sniffy, and feel sick -- how much does it really matter if it's actually the flu or not?