First, any vaccine is only as good as the number of participants. Even if your vaccine is a different strain than the type going around, the vaccine could lessen the seriousness of your strain should you get it.

Second, be certain you are not allergic to the assay used I.e., what the culture is grown in, such as eggs.

Third, make sure you are not sick when you receive the injection. You don't want to put anything foreign into an already compromised body.

Finally, people with a Neurological illness should take the injected "dead" virus, never the live virus delivered nasally

Source: two nurse anesthetist and a pharm rep (my kids)