[mennis16]

I've never heard the exhausting activities warning, but I do get mild flu-like symptoms for a few days (low grade fever, some fatigue, congestion) after the flu shot most years.

I don't know how common it is to experience this, as I would say I have a subpar immune system (frequently sick as a kid, history of food allergies, etc.). But when I've discussed it with doctors they do say my reaction is unsurprising, however the benefits outweigh the "costs".