I don't know about injections, but you can do a number of things to keep them at bay. These include using DEET (most bug repellents have this as an ingredient), wearing light colored, loose fitting clothing, don't camp near shallow standing water if possible, keep your tent screen closed and only open it to the extent that you need to get something and when you're ready to enter it to sleep. Catnip is supposed to work better than DEET and has no real side effects (like DEET may have) except for a possible allergic reaction. Vitamin B1 and lavender oil are also touted as effective repellents.
I still got 50 infected mozzie bites.
Someone mentioned to me that there is some sort of injection a person can get if they are allergic (as I seem to be) to mosquito bites. I just haven't been able to find out what it is yet.