Adverse Event Following Immunization (AEFI) with Anthrax Vaccine Adsorbed (AVA): Large Local Inflammatory Reaction Ana Reyes, DNP(1) Thomas Frank, MD(2) (1)DHA Immunization Healthcare Division, Pacific Region Clinical Team, San Diego, CA (2)Kirk Army Health Clinic, Aberdeen, MD Background: Anthrax Vaccine Adsorbed (AVA) is used to protect military service members from infection with Bacillus anthracis, a pathogen that has potential for use as a bioweapon. Although AVA is an effective and safe product, it is also reactogenic and can cause inflammatory reactions at the injection site in some vaccine recipients. The Defense Health Agency Immunization Healthcare Division (DHA IHD) has worked to reduce AVA adverse events following immunization (AEFIs) through studies on the dosing schedule and route of administration. In particular, DHA IHD compelled changes in the route of pre-exposure AVA administration, from subcutaneous to intramuscular (IM), as approved by the Food and Drug Administration in 2008. Although IM administration of AVA has decreased the occurrence of local adverse events, these reactions may still occur in AVA vaccine recipients. Case description: A 44-year-old active-duty male presented with erythema, swelling, and pain around the vaccine injection site within one day of receipt of AVA in his right deltoid. He reported associated fatigue, but no fever, no chest pain, no respiratory symptoms, no gastrointestinal symptoms, and no neurologic symptoms. He had full range of motion in his right arm with no perceived shoulder joint involvement. Erythema and swelling in his right upper arm progressed to an area larger than 15x10 cm size over two days following vaccination. Conservative treatment with nonsteroidal anti-inflammatory medication was associated with gradual resolution of all symptoms over the following seven days. Follow-up: DHA IHD clinicians were consulted, reviewed the differential diagnosis for this presentation, and concurred with the final diagnosis of large local inflammatory reaction following IM administration of AVA. This AEFI was appropriately reported to the Vaccine Adverse Event Reporting System. Although the reaction does not preclude future vaccination, efforts may be made to reduce the risk of future events. This service member had received 6 previous AVA doses without reported problems. Avoiding unnecessary booster doses, and potentially spacing any future booster intervals up to 3 years, may reduce the risk of recurrent local inflammatory reactions. Minimizing concomitant vaccinations, and ensuring anatomic spacing of co-administered injections, may also reduce risk. Finally, the service member may be reassured that local inflammatory reactions, while uncomfortable, do not represent “allergies” and will resolve within days of occurrence without sequelae.