Question: How do we code an adverse reaction to a COVID-19 vaccine that was noted by a physician in our practice? Illinois Subscriber Answer: The AHA ICD-10-CM Coding Clinic gave the following advice in Vol. 8, No. 1 (2021) on how to code adverse reactions to the COVID-19 vaccine. First, assign the code for the side effects: Depending on the patient, this could take the form of numerous conditions, such as R07.89 (Other chest pain), R09.89 (Other specified symptoms and signs involving the circulatory and respiratory systems), and R53.81 (Other malaise). Then, assign the code for the reaction: Again, this will depend on the patient’s individual circumstances. For an adverse reaction, you’ll use T50.B95A (Adverse effect of other viral vaccines, initial encounter). But if the patient goes into anaphylactic shock after receiving the vaccine, you’ll use T80.52XA (Anaphylactic reaction due to vaccination, initial encounter). Why? Even though the synonyms accompanying the T80.5- codes indicate that the codes should be used for anaphylactic shock after the patient has received a serum-based vaccine — and the COVID-19 vaccine is an mRNA vaccine and not serum-based — the Coding Clinic notes that “although subcategory T80.5, identifies anaphylactic reaction to serum, it is the closest available code to capture this condition.” Expert coding tip: The Coding Clinic article notes that even if the side effects are normal, “it would be appropriate to report a code(s) for side effects when the patient requires additional treatment or medical care such as monitoring or treatment for the side effects.”