M-S category	ICD-9 codes included
Physician-confirmed acute otitis media (AOM)	380.10, 382.11, 382.01, 382.02, 382.4, 382.9†
Physician-confirmed lower respiratory tract illness (LRTI)‡	165.0, 464.1, 464.10, 464.11, 464.2, 464.20, 464.21, 464.4, 466, 466.0, 466.1, 466.11, 466.19, 480.0, 480.1, 480.2, 480.3, 480.8, 480.9, 481, 482.0, 482.1, 482.2, 482.3, 482.30, 482.31, 482.32, 482.39, 482.4, 482.40, 482.41, 482.42, 482.49, 482.8, 482.81, 482.82, 482.83, 482.84, 482.89, 482.9, 483, 483.0, 483.1, 483.8, 484.1, 484.3, 484.5, 484.6, 484.7, 484.8, 485, 486, 487.0, 487.1, 487.8, 488.01, 488.02, 488.09, 488.11, 488.12, 488.81, 490, 518.0, 518.1, 518.2, 518.82, 519.11, 519.8, 786.0, 786.05, 786.07, 786.09, 786.1, 786.2, 786.6, 786.7
Physician-confirmed serious extra-pulmonary complications	729.1, 008.8, 070.9, 322, 322.0, 322.1, 322.2, 322.9, 323, 323.0, 323.01, 323.02, 323.1, 323.2, 323.4, 323.41, 323.42, 323.5, 323.51, 323.52, 323.6, 323.61, 323.62, 323.63, 323.7, 323.71, 323.72, 323.8, 323.81, 323.82, 323.9, 345, 345.0, 345.00, 345.01, 345.1, 345.10, 345.11, 345.2, 345.3, 345.4, 345.40, 345.41, 345.5, 345.50, 345.51, 345.60, 345.61, 345.7, 345.70, 345.71, 345.8, 345.80, 345.81, 345.9, 345.90, 345.91, 420, 420.0, 420.9, 420.90, 420.91, 420.99, 421, 421.0, 421.1, 421.9, 422, 422.0, 422.9, 422.90, 422.91, 422.92, 422.93, 422.99, 425, 425.0, 425.1, 425.2, 425.3, 425.4, 425.5, 425.7, 425.8, 425.9, 780.31, 780.32, 780.39

* All general terms for each criteria (i.e., LRTI: shortness of breath, pulmonary congestion, pneumonia, bronchiolitis, bronchitis, wheezing, or croup; extra-pulmonary complications: myositis, encephalitis, seizure, or myocarditis) were cross-checked with ICD-9 codes and the Centers for Disease Control and Prevention’s High-Risk Inpatient Influenza Vaccination Module.

^† Patient must have 382.9 code in addition to KP diagnosis descriptions that indicate acute (as opposed to chronic) otitis media.

‡ Patient must have 487.1 code in addition to KP diagnosis description of “Influenza with other respiratory manifestations”; patients with 487.1 and KP diagnosis descriptions of “Influenza-like illness” or “Influenza” were classified as having mild influenza.

ICD-9: International Classification of Diseases, Ninth Revision.