If one has time, this documentary on SBS is worth watching for a balanced view on the risks of vaccinating and not vaccinating.
Like any medical treatment, there are risks and potential side effects. With vaccinations, there are some in the community which experience some undesirable side effects as well as many others who experience none. Severe side effects are rare, however the risks of getting a preventable disease is real.
Influenza is one of the most common diseases and every year many have severe complications from this infection. Vaccinations are one way to reduce risks and potential complications from some of the most virulent strains.
The flu vaccination also only protects against those strains covered by the vaccination.