Probably Modifier 25 with 99391.
If your physician administers vaccines on the same day as a well visit, report the preventive visit with the appropriate code such as 99391 and separately report the appropriate immunization administration code (such as 90460). Although not required by CPT®, you might need to append modifier 25 to the preventive medicine code, depending on the payer's guidelines.
Example: A pediatrician performs a complete well visit on a 15-month-old patient, and counsels the mother on vaccine risks and benefits prior to giving the patient a DTaP-vaccination. The diphtheria, tetanus and pertussis each count as one component. For the vaccine administration with counseling on the components included in the DTaP, report one unit of 90460 (Immunization administration through 18 years of age via any route of administration, with counseling by physician or other qualified health care professional; first vaccine/toxoid component) and two units of +90461 (Immunization administration through 18 years of age via any route of administration, with counseling by physician or other qualified health care professional; each additional vaccine/toxoid component). You'll also report the appropriate preventive medicine code, such as 99391. You'll link V20.2, Routine infant or child health check to all of the codes billed, because vaccinations link well to V20.2 and you do not need to link the vaccines to a separate ICD-9 code. Therefore, your claim will look like this:
90460 linked to V20.2
90461 x 2 linked to V20.2
90700 (Diphtheria, tetanus toxoids, and acellular pertussis vaccine [DTaP], when administered to individuals younger than 7 years, for intramuscular use) linked to V20.2
99391-25 linked to V20.2
3. Additional Injections
You may perform a well child visit that doesn't require vaccine administration, but does require other injections. In these cases, you should still report the injection code with the preventive medicine visit.
For example: Your nurse administers a Synagis injection to a premature baby during a well child visit. In this situation, you'll report the appropriate preventive medicine code with modifier 25 appended, along with 96372 (Therapeutic, prophylactic, or diagnostic injection [specify substance or drug]; subcutaneous or intramuscular) to complete the claim.
Link your Synagis diagnosis to 765.10 (Prematurity), and link the preventive visit code to V20.2.
Don't forget: If you are paying for the Synagis, you should also bill for the product. Report 90378 (Respiratory syncytial virus, monoclonal antibody, recombinant, for intramuscular use, 50 mg, each).