I just vaccinated my new chicks for Cocci. You don't have to inject them, you spray the vaccine on their food. I got my vaccine from First State Vet supply Peter Brown the owner is a PHD in Poultry Science and extreamly helpful. He will instruct you in how to vaccinate for any of the meds her carries. I don't know about Mareks, I have not done it, but I think it is an injection, not sure. Good Luck