We get this question quite often, and it would be convenient to combine the treatments to save on an additional call fee.  However, we generally recommend against this for a few reasons.  One of the drugs we typically use in joint injections is a steroid anti-inflammatory such as triamcinolone or methylprednisolone acetate.  These are very potent anti-inflammatory agents, and can cause immune suppression even in the small amounts used in joints.  This means that the immune response to a vaccine could be dampened by the steroids injected in the joint, and the horse may not be adequately protected by the vaccine if it is administered at the same time as intra-articular injections.  Also, in the case of the intranasal Strangles (Strep equi) vaccine, we are very careful not to have contamination of any injection sites with the snorting of the vaccine after the horse is given this vaccine.  If this modified live bacteria is inadvertently injected, it can set up a nasty abscess and this would be particularly devastating if this infection were to occur in a joint.